CN1330005C - Ultraviolet reinforced photo detector employing gallium arsenide base phosphorated material and making method - Google Patents

Abstract

The invention relates to an ultraviolet-enhanced photodetector based on gallium arsenide-based phosphorus-containing compound semiconductor materials and a manufacturing method, which is characterized in that a semi-insulating gallium arsenide single crystal material is used as the substrate of the detector, and a specific detector is grown on it by an epitaxial method. The wide bandgap phosphorus-containing compound thin film material is used as the active light absorption layer and window layer to achieve the effect of ultraviolet enhanced light absorption and eliminate its response to infrared light, and a PN junction is formed in it by a suitable doping method. The epitaxial material uses a specific selective etching process to produce a mesa structure, and after passivation protection, the contact electrode is produced, and the corresponding anti-reflection and anti-reflection coating is selected to further improve its short-wave response. This kind of photodetector can be used in flame detection, photometric measurement in ultraviolet and visible light bands, tail flame tracking, biological and chemical gas detection, ultraviolet protection, etc., and can be monolithic or mixed with infrared photodetectors to form a two-color detector.

Description

Ultraviolet-enhanced photodetector using gallium arsenide-based phosphorus-containing material and manufacturing method

technical field

The invention relates to an ultraviolet-enhanced photodetector using a gallium-based phosphorus-containing compound semiconductor material and a manufacturing method. More precisely, the invention provides a new type of photodetector, which can make the photodetector have a good response in the ultraviolet to visible light band , while sufficiently suppressing the infrared light response. The invention belongs to the technical field of semiconductor optoelectronic materials and devices.

Background technique

As a typical optoelectronic device, semiconductor photodetectors have been widely used in many occasions, and their operating bands have been extended from visible to near-infrared to mid-infrared and even far-infrared. As one of the most commonly used photodetectors, silicon photodiodes have good performance in the visible light to near-infrared band (λ<1.1 μm). Some special process technologies can also extend the response wavelength to the ultraviolet band. However, due to the Due to the limitations of the working principle and material properties, the response to the long-wave direction is significantly greater than the short-wave response. For some special applications, it is often required that the detector has a higher response in the short-wave direction and suppress its response in the long-wave direction to avoid interference, etc. For silicon photodetectors, this requires a more complex filter. Optical structure, at the cost of sacrificing a certain short-wave response and increasing costs, the overall performance of the system will also be greatly limited. Since various new materials, especially semiconductor materials, were widely used in the 1960s, optoelectronic devices based on semiconductor materials have made great progress, and material growth technology has also continued to improve. They have precise control capabilities and are suitable for growing complex structures. Growth technologies such as molecular beam epitaxy (MBE) and metal organic vapor phase epitaxy (MOVPE) have begun to be widely used, and various commercial growth equipment have also been introduced to the market, making it possible to use new material systems to meet different requirements. The present inventors provide a novel photodetector that meets the aforementioned requirements by selecting a new material system.

Contents of the invention

The purpose of the present invention is to provide an ultraviolet enhanced photodetector using gallium arsenide-based phosphorus-containing materials and a manufacturing method, that is, to provide a newly fabricated ultraviolet enhanced photodetector, which completely eliminates its infrared radiation by using the inherent characteristics of the material. light response. And the detector has high quantum efficiency, fast response speed, high reliability and radiation resistance. This kind of photodetector can be used in flame detection, photometric measurement in ultraviolet and visible light bands, tail flame tracking, biological and chemical gas detection, ultraviolet protection, etc., and can be integrated with infrared photodetectors to form a two-color detector for special occasions . The working principle of the present invention and its implementation are universal,

According to the problems existing in the above technical background and reality, the present invention determines the material system of the detector and develops a corresponding material growth process. The cut-off wavelength of semiconductor photodetectors (quantum detectors) in the long-wave direction is determined by the bandgap of the material in the active region of the detector. In order to eliminate the response of the detector to infrared light, the present invention selects a substrate with GaAs The lattice-matched phosphorus-containing wide-bandgap material system is used as the active region material of the detector. The cost of using gallium arsenide as the substrate material is relatively low, and the material is relatively mature, quality and supply are guaranteed. For applications such as the production of two-color detectors, the present invention selects undoped semi-insulating gallium arsenide material as the substrate, and uses epitaxially grown wide-bandgap phosphorus-containing compound films on it as the active light absorption layer and window layer , and a PN junction is formed between the absorption layer and the window layer, and the detector is led out by a single-sided electrode, so that the substrate is transparent to infrared light (λ>870nm to the mid- and far-infrared band), and can be integrated during integration. It does not affect the performance of the lower detector. On the other hand, it is opaque to short-wavelength (λ<870nm) light, and can play a good role as a short-wave cut-off filter for the lower detector, fully suppressing the short The wavelength (λ<870nm) light response, so in many occasions do not need additional filters. Another advantage of using gallium arsenide substrate is that it can be monolithically integrated with the quantum well infrared detector to form a monolithic two-color or multi-color detector. For general applications, a highly doped N-type conductive substrate can also be used. At this time, the detector can adopt a double-sided electrode structure.

Phosphorus-containing wide-bandgap material systems that match the lattice of GaAs substrates include ternary Ga _0.51 In _0.49 P, Al _0.52 In _0.48 P and quaternary (Al _z Ga _1-z ) _0.51 In _0.49 P etc., Ga _0.51 In _0.49 P is a direct band gap material, the band gap at room temperature is 1.85eV, (Al _z Ga _1-z ) _0.51 In _0.49 P is also a direct band gap material when 0<z<0.55, its band gap The gap is adjustable between 1.85-2.26eV with the increase of z, and the corresponding cut-off wavelength can be changed between 670-550nm. Al _0.52 In _0.48 P is an indirect bandgap material, and its bandgap is 2.34eV, so it can be adjusted according to the detector The difference in cutoff wavelength requires tailoring of the relative compositions of Al and Ga. In this material system, materials with different components are selected as the light absorbing layer and the window layer respectively. One solution is to use the ternary system GaInP with a relatively small band gap as the light absorbing layer, and the ternary system AlInP with a large band gap as the light absorbing layer. The window layer is used to achieve high quantum efficiency and low dark current performance, and the low refractive index of AlInP is used to control the thickness of the window layer to achieve a certain effect of anti-reflection and enhanced short-wave response. The use of wide-bandgap materials can greatly increase the output voltage of the detector under illumination, and the short-wave response can also be significantly improved. This material system also has excellent radiation resistance. The detector uses molecular beam epitaxy (MBE) or metal organic vapor phase epitaxy (MOVPE) to grow epitaxial materials, and controls the doping when growing the active light absorbing layer and window layer to grow low-doped and The highly doped region forms a PN junction. We selected a thinner highly doped layer thickness in the growth process to ensure the high responsivity and good short-wave response of the detector. This UV-enhanced photodetector can adopt the following epitaxial structure: semi-insulating gallium arsenide material (or silicon-doped low-resistance gallium arsenide material) is used as the substrate, and a layer of n-type highly doped (n>5 ×10 ¹⁷ cm ^-3 ) lower contact layer (this contact layer can be silicon-doped gallium arsenide material, which also serves as an epitaxial buffer layer), and then grow low-doped or unintentionally doped (n<5 × ^{10 17} cm ^-3 ) phosphorus-containing wide-bandgap light ^- absorbing layer, and then grow a phosphorous-containing wide-bandgap light-absorbing layer (also A window layer may be included at the same time), and finally grow a p-type highly doped (p>5×10 ¹⁷ cm ^-3 ) upper contact layer (this contact layer may be beryllium-doped gallium arsenide material).

On the basis of growing high-quality detector materials, the invention develops a detector manufacturing process and a selective etching process. In the detector manufacturing process, we have adopted a special selective etching formula. Since the upper and lower contact layers in the device structure are low-resistance GaAs materials that do not contain phosphorus, the present invention utilizes the non-phosphorus-containing material of the contact layer and the active light absorption layer and According to the different chemical characteristics of the phosphorus-containing materials in the window layer, the mesa structure of the detector is etched by a wet selective etching process, and then a self-aligned light-transmitting window is produced. In the actual process, we use a tartaric acid-based etching solution (such as tartaric acid/hydrogen peroxide system) to etch GaAs materials, when it encounters phosphorus-containing compound materials, the etching will automatically stop, use hydrochloric acid-based etching solution (such as hydrochloric acid/phosphoric acid system) to etch phosphorus-containing compounds, and when encountering phosphorus-free materials, it will etch It will also stop automatically, which greatly facilitates the process control. The tartaric acid/hydrogen peroxide system is composed of tartaric acid and water diluted at a volume ratio of 1:1 and then added with 5 vol% hydrogen peroxide; the volume ratio of hydrochloric acid/phosphoric acid is 1:4, and the hydrochloric acid used is chemically pure or analytically pure.

According to the requirements of the enhanced ultraviolet response spectrum of the detector, in the detector process, we selected a low refractive index material transparent to ultraviolet light as the anti-reflection coating material, and adopted a thinner anti-reflection anti-reflection coating according to the requirement of increasing the short-wave response. Good UV enhancement effect can be achieved. The actual device manufacturing process steps are as follows: First, the epitaxial structure of the ultraviolet-enhanced photodetector of the gallium arsenide-based phosphorus-containing material is grown. After cleaning, the surface is passivated and the light entrance window is engraved on the passivation layer, and then the electrode pattern is photoetched, and the contact electrode is produced by evaporation and stripping. After alloying, the GaAs on the light entrance window is removed by selective etching. The upper contact layer, and then use the evaporation method to make anti-reflection and anti-reflection film and remove its unnecessary parts, and finally obtain the detector core after substrate thinning and polishing, scribing, chipping and other processes. After preliminary screening, the detector dies are packaged accordingly as required, and then performance tests are performed.

The refractive index range of the anti-reflection coating material is 1.8-1.9, such as one of ZrO ₂ or Al ₂ O ₃ .

The growth of the epitaxial structure comprises:

(1) First grow a highly doped Si n-type low-resistance GaAs lower contact layer on the GaAs substrate;

(2) growing a low-doped Si or non-doped Si-containing phosphorous compound light absorbing layer on the lower contact layer grown in step (1);

(3) growing a light absorbing layer of a P-type phosphorus-containing compound highly doped with Be on the absorption layer grown in step (2), and then growing a highly doped P-type phosphorus-containing compound window layer thereon;

(4) Finally, on the window layer grown in step (3), a highly doped P-type low-resistance GaAs upper contact layer is grown;

This new type of UV-enhanced photodetector can play an important role in flame detection, photometry, tail flame tracking, biological and chemical gas detection, and ultraviolet protection. For example: the spectral response of the detector (as shown in embodiment 1 and accompanying drawing 4) that adopts AlInP/GaInP/GaAs epitaxial structure is very consistent with the visual sensitivity spectral response (and standard C.I.E curve) of human eyes, so this detector can It is directly applied to illuminance measurement; another example: this detector has a good response in blue and green light wavelengths and extends to the near ultraviolet band, so it is also suitable for tail flame tracking (such as missile two-color guidance) and flame detection devices.

Description of drawings

FIG. 1 is a schematic diagram of an ultraviolet-enhanced photodetector based on gallium arsenide-based phosphorus-containing compound semiconductor materials provided by the present invention. In the figure 1: semi-insulating gallium arsenide substrate, 2: wide band gap containing phosphorescent absorbing layer, 3: window layer, 4: PN junction, 5: passivation layer, 6: lower contact layer, 7: lower electrode, 8 : upper electrode, 9: AR coating, 10: upper contact layer

Fig. 2 is the typical I-V characteristic of the AlInP/GaInP/GaAs ultraviolet enhanced photodetector made according to embodiment 1

Fig. 3 is the I-V characteristic of the AlInP/GaInP/GaAs ultraviolet enhanced photodetector made according to embodiment 1 near zero bias voltage

Fig. 4 is the response spectrum of the AlInP/GaInP/GaAs ultraviolet enhanced photodetector made by embodiment 1 (the dotted line is the C.I.E curve of the human eye visual sensitivity standard)

Detailed ways

The substantive features and remarkable progress of the present invention are further described below through the embodiments of the accompanying drawings, but the present invention is by no means limited, that is, the present invention is by no means limited to the embodiments.

Example 1:

Al _0.52 In _0.48 P/Ga _0.51 In _0.49 P/GaAs UV-Enhanced Photodetectors Grown by Gas Source Molecular Beam Epitaxy (GSMBE)

1. Production and implementation steps:

1. Al _0.52 In _0.48 P/Ga _0.51 In _0.49 P/GaAs UV-enhanced photodetector materials were grown by gas source molecular beam epitaxy (GSMBE). Firstly, the growth process of Ga _0.51 In _0.49 P and Al _0.52 In _0.48 P single-layer materials is determined according to the lattice matching conditions, and the Ga The beam source temperature of Al and Al can control the mismatch between GaInP and AlInP single-layer materials and GaAs substrate at about +5×10 ^-4 , and control the growth rate at 0.5-1 μm/h. During this process, the Be doping temperature is determined at the same time so that the carrier concentration is greater than 1E18cm ^-3 .

2. Grow the device structure of the detector under optimized growth conditions. First grow a high-doped Si (n>5×10 ¹⁷ cm ^-3 ) n-type low-resistance GaAs lower contact layer with a thickness of 0.8-1.5 μm, and grow a low-doped Si (n<5×10 ¹⁷ cm ^-3 ) or undoped n-type Ga _0.51 In _0.49 P light absorbing layer, the specific thickness can be determined according to the specific device requirements (thinner epitaxial layer can be used when it is desired to suppress long-wave response, but the quantum efficiency will be reduced) and then grow a p-type Ga ^0.51 In ^0.49 P _light absorbing layer with a thickness of 30nm on it, and then grow _a highly doped Be ( p>5×10 ¹⁷ cm ^-3 ) p-type Al _0.52 In _0.48 P window layer, and finally grow a high-doped Be (p>5×10 ¹⁷ cm ^-3 ) p-type low-resistance GaAs upper contact with a thickness of 0.2-0.5 μm layer.

3. After the grown epitaxial wafer is qualified by microscope inspection, structural characteristics (X-ray measurement of lattice matching, etc.) and electrical characteristics (electrochemical C-V measurement of carrier concentration, etc.), the device process is carried out. First use photolithography to carve out the mesa pattern, use selective etching to etch the mesa structure, passivate the surface after cleaning and carve the light entrance window on the passivation layer, and then photoetch the electrode pattern, use evaporation and stripping The method is to make the contact electrode, remove the GaAs upper contact layer on the light entrance window by selective etching after alloying, then make the anti-reflection and anti-reflection film by evaporation method and remove its unnecessary part, and finally polish it by thinning the substrate , scribing, chipping and other processes to obtain the detector core.

4. The detector core is preliminarily screened and packaged accordingly as required to make a detector.

Second, the characteristics of the detector:

Figure 2 shows the typical IV characteristics of the Al _0.52 In _0.48 P/Ga _0.51 In _0.49 P/GaAs UV-enhanced photodetector fabricated by the above process, the breakdown voltage is >5V, and the dark current under 0.5V reverse bias is less than 5pA Figure 3 shows its IV characteristics near zero bias voltage, and its zero bias resistance R ₀ is as high as 8×10 ⁴ MΩ. Figure 4 is the response spectrum of the detector, the response wavelength range is 250-650nm, and the peak response wavelength is about 580nm. Compared with silicon photodetectors, the detector provided in this embodiment has been completely suppressed in response to infrared light. The output voltage is also greatly improved.

Example 2:

Growth of Al _0.52 In _0.48 P/Al _0.28 Ga _0.23 In _0.49 P/GaAs UV-enhanced photodetectors grown by GSMBE growth method

Production implementation steps:

1. Al _0.52 In _0.48 P/Al _0.28 Ga _0.23 In _0.49 P/GaAs UV-enhanced photodetector materials were grown by gas source molecular beam epitaxy (GSMBE). Firstly, the growth process of Al _0.28 Ga _0.23 In _0.49 P and Al _0.52 In _0.48 P single-layer materials is determined according to the lattice matching conditions. Under the conditions of substrate temperature of 470°C, P source pressure of 450 Torr and In beam source temperature of 850°C Determine the beam source temperature of In, Ga and Al so that the mismatch between AlGaInP and AlInP single-layer materials and GaAs substrate is controlled at about +5×10 ^-4 , and the growth rate is controlled at 0.5-1 μm/h. During this process, the Be doping temperature is determined at the same time so that the carrier concentration is greater than 1E18cm ^-3 .

2. Grow the device structure of the detector under optimized growth conditions. First grow a high-doped Si (n>5×10 ¹⁷ cm ^-3 ) n-type low-resistance GaAs lower contact layer with a thickness of 0.8-1.5 μm, and grow low-doped Si with a thickness of 0.5-1 μm (according to specific device requirements) on it (n<5×10 ¹⁷ cm ^-3 ) or undoped n-type Al _0.28 Ga _0.23 In _0.49 P light absorbing layer, and then grow highly doped Be (p>5×10 ¹⁷ cm ^{-3 )} with a thickness of 30nm on it ³ ) p-type Al _0.28 Ga _0.23 In _0.49 P light absorbing layer, and then grow a highly Be-doped (p>5×10 ¹⁷ cm ^-3 ) p-type Al _0.52 In _0.48 P window layer with a thickness of 20-30 nm on it, Finally, a high-doped Be (p5×10 ¹⁷ cm ^-3 ) p-type low-resistance GaAs upper contact layer is grown with a thickness of 0.2-0.5 μm.

3. After the grown epitaxial wafer is qualified by microscope inspection, structural characteristics (X-ray measurement of lattice matching, etc.) and electrical characteristics (electrochemical C-V measurement of carrier concentration, etc.), the device process is carried out. First use photolithography to carve out the mesa pattern, use selective etching to etch the mesa structure, passivate the surface after cleaning and carve the light entrance window on the passivation layer, and then photoetch the electrode pattern, use evaporation and stripping The method is to make the contact electrode, remove the GaAs upper contact layer on the light entrance window by selective etching after alloying, then make the anti-reflection and anti-reflection film by evaporation method and remove its unnecessary part, and finally polish it by thinning the substrate , scribing, chipping and other processes to obtain the detector core.

4. The detector core is preliminarily screened and packaged accordingly as required to make a detector.

It has been determined that the cut-off wavelength of the Al _0.52 In _0.48 P/Al _0.28 Ga _0.23 In _0.49 P/GaAs UV-enhanced photodetector produced by the above process is comparable to that of the Al _0.52 In _0.48 P/Ga _0.51 In _0.49 P/GaAs UV-enhanced photodetector If it is further reduced, the detector's response to infrared light can be completely suppressed, and the response to red light can also be partially suppressed, and the ultraviolet enhancement effect can be further strengthened.

Claims (9)

1, a kind of ultraviolet reinforced photo detector that adopts gallium arsenide base phosphorated material, it is characterized in that adopting the semi-insulating GaAs monocrystal material of doping as substrate of detector, adopt epitaxially grown broad stopband phosphorus-containing compound film as active light absorbing zone and Window layer thereon, and between absorption window and Window layer, constitute PN junction, and adopt single-side electrode to draw.

2, by the ultraviolet reinforced photo detector of the described employing gallium arsenide base phosphorated material of claim 1, it is characterized in that described broad stopband phosphorus-containing compound is the Ga of ternary system _0.51In _0.49P, Al _0.52In _0.48(the Al of P or quaternary system _zGa _1-z) _0.51In _0.49P, 0＜Z＜0.55.

3, by the ultraviolet reinforced photo detector of the described employing gallium arsenide base phosphorated material of claim 2, it is characterized in that described Ga _0.51In _0.49P, Al _0.52In _0.48P is the direct band gap material, and the band gap material under the room temperature is 1.85eV; (Al _zGa _1-z) _0.51In _0.49P is an indirect bandgap material, and band gap is 2.34eV.

4, by the ultraviolet reinforced photo detector of the described employing gallium arsenide base phosphorated material of claim 1, it is characterized in that as substrate of detector be highly doped N type conductive substrates, detector adopts the double-face electrode structure.

5, make the method for the ultraviolet reinforced photo detector of employing gallium arsenide base phosphorated material as claimed in claim 1, it is characterized in that concrete making step is:

(1) at first on the GaAs substrate growth highly doped Si n type low-resistance GaAs under contact layer;

(2) the phosphorus-containing compound light absorbing zone of the low-doped Si of growth or the Si that undopes on the following contact layer of step (1) growth;

(3) light absorbing zone of the P type phosphorus-containing compound of the highly doped Be of growth on the absorbed layer of step (2) growth, the compound Window layer that the P type of growing highly doped thereon then is phosphorous;

(4) at last on the Window layer of step (3) growth the highly doped P type low-resistance GaAs of growth go up contact layer;

(5) carrying out device technology at the good epitaxial wafer of step (1)～(4) growths after after testing makes, adopt photoetching method to carve the table top figure earlier, etch mesa structure with the selective etching method, after cleaning, carry out surface passivation and on passivation layer, carve light portal, make electrode pattern again by lithography, adopt evaporation and stripping means to produce contact electrode, GaAs through removing on the light portal with the selective etching method after the alloying goes up contact layer, make the antireflection anti-reflection film and remove its unwanted part with method of evaporating then, after the substrate thinning polishing, scribing, obtain probe dice after the technologies such as disintegrating tablet;

(6) probe dice encapsulates after Preliminary screening as required accordingly, makes detector.

6, press the manufacture method of the ultraviolet reinforced photo detector of the described employing gallium arsenide base phosphorated material of claim 5, it is characterized in that in epitaxial wafer growth step (1)～(4):

(1) contact layer thickness is 0.8-1.5 μ m under the n type of described highly doped Si, and doping content is greater than 5 * 10 ¹⁷Cm ^-3

(2) described low-doped Si or plain n type phosphorus-containing compound, light absorption thickness is 0.5-1 μ m, low-doped Si concentration is less than 5 * 10 ¹⁷Cm ^-3

(3) described on the light absorbing zone of the low-doped Si or the Si that undopes the regeneration P type phosphorus-containing compound thickness of mixing Be that grows tall be 30nm, the concentration of doping Be is greater than 5 * 10 ¹⁷Cm ^-3

(4) described Window layer is the high p type phosphorus-containing compound of mixing Be, and growth thickness is 20-30nm, and the concentration of doping Be is greater than 5 * 10 ¹⁷Cm ^-3

(5) described upward contact layer thickness is 0.2-0.5 μ m, and the concentration of doping Be is greater than 5 * 10 ¹⁷Cm ^-3

7, press the manufacture method of the ultraviolet reinforced photo detector of claim 5 or 6 described employing gallium arsenide base phosphorated materials, it is characterized in that epitaxial growth is a kind of in employing molecular beam epitaxy or the gas phase epitaxy of metal organic compound method.

8, press the manufacture method of the ultraviolet reinforced photo detector of claim 5 or 6 described employing gallium arsenide base phosphorated materials, the material that it is characterized in that light absorbing zone is Ga _0.51In _0.49P or (Al _zGa _1-z) _0.51In _0.49P, a kind of in 0＜Z＜0.55, window material is Al _0.52In _0.48P, the refractive index of anti-reflection film material is the ZrO of 1.8-1.9 ₂Or Al ₂O ₃In a kind of.

9, press the manufacture method of the ultraviolet reinforced photo detector of the described employing gallium arsenide base phosphorated material of claim 5, utilize tartaric acid/hydrogen peroxide corrosive liquid etching GaAs material when it is characterized in that selective etching, etching stops automatically when running into the phosphorus-containing compound material; Utilize hydrochloric acid/phosphoric acid system etching phosphorus-containing compound, etching stops automatically when running into not phosphorus-containing compound.