CN106946212A - A kind of surface quantum point humidity sensor chip - Google Patents

Abstract

It is an object of the present invention to provide a kind of surface quantum point humidity sensor chip, including GaAs from bottom to top（GaAs）Substrate layer, N-shaped GaAs cushions, bury InGaAs quantum dot layers and InGaAs surface quantums point layer, bury and be deposited with the first silicon dioxide passivation layer on InGaAs quantum dot layer left end steps, bury and be deposited with the second silicon dioxide passivation layer on InGaAs quantum dot layer right-hand member steps, the lower right side of second silicon dioxide passivation layer is deposited with the 3rd silicon dioxide passivation layer on N-shaped GaAs cushions, Au/Ge/Ni alloy bottom electrodes are deposited with above 3rd silicon dioxide passivation layer, InGaAs surface quantums point layer has the 4th silicon dioxide passivation layer above the left side, deposition has Au/Ge/Ni alloy Top electrodes in 4th silicon dioxide passivation layer；The present invention is simple in construction, and prepared by production convenient, and low cost, effect is good, and economic and social benefit is notable.

Description

A surface quantum dot humidity sensor chip

technical field

The invention relates to a semiconductor electronic device, in particular to a surface quantum dot humidity sensor chip.

Background technique

Quantum dots are also called semiconductor nanocrystals. Compared with bulk materials, they have small size, large specific surface area, high surface energy, and large surface atomic ratio. When the particle size is smaller than the exciton Bohr radius, the electronic state of the particle will occur. Mutation, thus showing the basic small size effect, surface effect, quantum effect and macroscopic quantum tunneling effect; due to its unique photoelectric properties, such as high quantum yield, long fluorescence lifetime, large extinction coefficient, strong light resistance Receptivity, narrow emission spectrum and wide excitation spectrum, etc., the preparation and application of quantum dots have attracted widespread attention; especially in the field of sensing, quantum dots have been used to build sensors, such as ion sensors, biosensors, Fluorescent probes, medical imaging and gas sensors, etc.

The preparation methods of quantum dots mainly include two kinds of physical preparation method and chemical preparation method. The chemical preparation method is mainly used to synthesize quantum dot materials such as CdSe, ZnS, CdS, CdTe, HgS, etc., but these quantum dot materials are different from the current silicon-based and There are enormous challenges in the integration of widely used optoelectronic devices such as GaAs-based. In contrast, III-V quantum dots prepared by physical methods such as MOCVD and MBE have natural advantages in system integration, such as InGaAs and InP quantum dots, which have been widely used in lasers, infrared detectors, solar cells, etc. field.

In the above-mentioned quantum dot devices, in order to improve the performance of the device, it is often necessary to cover a layer of wide-bandgap semiconductor material (capping layer) on the surface of the quantum dots, such as covering a layer of GaAs on the surface of the InGaAs quantum dots to suppress the impact of the surface state on the quantum dots. The influence of the optical performance and electrical performance of the dot device; if the cap layer is not covered on the surface of the quantum dot, the surface quantum dot is formed. There are a large number of dangling bonds on the surface of surface quantum dots, forming surface states. The surface states have an adsorption effect on H ₂ O molecules, which inhibits the non-radiative recombination of the surface states, thereby affecting the optical and electrical properties of the surface quantum dots. Therefore, using In(Ga)As surface quantum dots as a sensitive material, using the influence of surface states on the optical and electrical properties of quantum dots, it is easy to realize the system integration and on-chip integration of water molecule detection, and realize the sensory measurement of humidity in the air .

However, the current quantum dot sensors mainly use single-layer quantum dots, and there are still the following difficulties in their application to humidity sensing. (1) Quantum dots such as CdSe, ZnS, CdS, CdTe, and HgS are difficult to integrate with current GaAs-based optoelectronic devices , which is not conducive to the development of on-chip systems and integrated systems; (2) supporting excitation light sources and optical detectors are required, which greatly increases the complexity and cost of sensors; (3) the performance of single-layer quantum dots is not optimized enough, such as The size uniformity of quantum dots is poor, the luminous intensity is weak, and the luminous spectral bandwidth is large.

Contents of the invention

In view of the above situation, in order to overcome the defects of the prior art, the purpose of the present invention is to provide a surface quantum dot humidity sensor chip, which can effectively solve the problem of poor uniformity of quantum dot size, weak luminous intensity and spectral bandwidth of the existing single-layer quantum dot humidity sensor. Larger, complex to use, less-than-satisfactory issues.

The technical scheme solved by the present invention is that the present invention includes a bottom-up GaAs (gallium arsenide) substrate layer, an n-type GaAs buffer layer, a buried InGaAs quantum dot layer and an InGaAs surface quantum dot layer, and the buried InGaAs quantum dot layer and the n-type The left and right ends of the n-type GaAs buffer layer are all in a stepped structure, and a vertical first silicon dioxide passivation layer is deposited on the left end step of the buried InGaAs quantum dot layer, and the first silicon dioxide passivation layer is connected with the n-type GaAs buffer layer. The end face of the layer is even, and a vertical second silicon dioxide passivation layer is deposited on the right end step of the buried InGaAs quantum dot layer, and the right lower part of the second silicon dioxide passivation layer is deposited on the n-type GaAs buffer layer. The third silicon dioxide passivation layer in the lateral direction, the Au/Ge/Ni alloy lower electrode connected to the n-type GaAs buffer layer is deposited on the third silicon dioxide passivation layer, and the quantum dot layer on the left side of the InGaAs surface has a layer with The first silicon dioxide passivation layer is connected to the lateral fourth silicon dioxide passivation layer, and the Au/Ge/Ni alloy upper electrode connected to the InGaAs surface quantum dot layer is deposited on the fourth silicon dioxide passivation layer .

The invention has the advantages of simple structure, convenient production and preparation, low cost and good effect. The presence of multi-layer buried quantum dots in the structure makes the humidity sensor more sensitive and has remarkable economic and social benefits.

Description of drawings

Fig. 1 is the front view of the sectional structure of the present invention.

detailed description

The specific implementation manners of the present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, the present invention includes a bottom-up GaAs (gallium arsenide) substrate layer 1, an n-type GaAs buffer layer 2, a buried InGaAs quantum dot layer 3 and an InGaAs surface quantum dot layer 4, and the buried InGaAs quantum dot layer 3 is covered with a layer of GaAs, the buried InGaAs quantum dot layer 3 and the left and right ends of the n-type GaAs buffer layer 2 are in a stepped structure, and the left end step of the buried InGaAs quantum dot layer 3 is deposited with a vertical first silicon dioxide passivation layer. layer 5, and the first silicon dioxide passivation layer 5 is flush with the end face of the n-type GaAs buffer layer 2, and a vertical second silicon dioxide passivation layer 8 is deposited on the right end step of the buried InGaAs quantum dot layer 3, On the lower right side of the second silicon dioxide passivation layer 8, a lateral third silicon dioxide passivation layer 7 is deposited on the n-type GaAs buffer layer 2, and a third silicon dioxide passivation layer 7 is deposited on the third silicon dioxide passivation layer 7. The Au/Ge/Ni alloy lower electrode 10 connected with the n-type GaAs buffer layer 2, the fourth silicon dioxide passivation layer connected with the first silicon dioxide passivation layer 5 on the left side of the InGaAs surface quantum dot layer 5 An Au/Ge/Ni alloy upper electrode 9 communicating with the InGaAs surface quantum dot layer 4 is deposited on the fourth silicon dioxide passivation layer 6 .

In order to ensure the effect and convenience of use,

The buried InGaAs quantum dot layer 3 is 1-15 layers (5 layers are given in the figure).

The thickness of each layer 3 of the buried InGaAs quantum dot layer is not greater than 20nm.

The chip is circular.

In the specific implementation of the present invention,

1. The n-type GaAs buffer layer is grown on a gallium arsenide substrate by molecular beam epitaxy;

2. The buried InGaAs quantum dot layer is grown on the n-type GaAs buffer layer by molecular beam epitaxy, and the thickness of each buried InGaAs quantum dot layer is 20nm;

3. The InGaAs surface quantum dot layer is grown on the buried InGaAs quantum dot layer by molecular beam epitaxy;

4. The step is etched between the n-type GaAs buffer layer and the buried InGaAs quantum dot layer using a wet etching process;

5. The silicon dioxide passivation layer is deposited on the etched steps;

6. The upper electrode of the Au/Ge/Ni alloy and the lower electrode of the Au/Ge/Ni alloy are photoetched on the silicon dioxide passivation layer, and lead holes are etched, and the Au/Ge/Ni alloy is evaporated in the lead holes. Made of Ni;

Compared with the prior art, the present invention has the following beneficial technical effects:

(1) Using InGaAs surface quantum dots as a sensitive material, it is easy to realize integration with existing GaAs-based optoelectronic devices, which is conducive to improving the integration of on-chip systems, and can lay the foundation for the realization of multi-functional on-chip integrated systems;

(2) By growing a layer of surface InGaAs quantum dots on the multi-layer buried quantum dots, the density and size of the surface quantum dots can be independently controlled, and the uniformity of the quantum dots can be improved. For example, when the number of buried quantum dot layers is 8, the average height of the surface quantum dots is 6.7±0.7 nm, and the average diameter is 46±1.8 nm, while when the number of buried quantum dot layers is 1, the average height of the surface quantum dots is 6.7 nm. ±1.3 nm, with an average diameter of 46±6nm.

(3) Utilizing the strong coupling between multi-layer buried quantum dots and surface quantum dots, this structure does not require supporting excitation light sources and optical detectors, and only needs to directly measure the resistance value between the upper and lower electrodes to realize environmental protection. The measurement of humidity has the advantages of simple structure and low cost. The low cost is specifically reflected in the fact that the price of the excitation light source (such as a 100mW laser with an excitation wavelength of 532nm) on the market is about 9,000 yuan, and the price of an optical detector (such as an InGaAs detector) is about 15,000 yuan. This structure does not require matching excitation light sources and optical detectors, which can save about 24,000 yuan in cost.

(4) Compared with single-layer surface quantum dots, the existence of multi-layer buried quantum dots in this structure makes the humidity sensor more sensitive, and the more layers of buried quantum dots, the higher the sensitivity. For example, the test results show that when the ambient humidity is 30%, the response current of the structure containing only one layer of buried quantum dots is 2.3 microamps, the response current of the structure containing five layers of buried quantum dots is 11.6 microamps, and the response current of the structure containing ten layers of buried quantum dots is 11.6 microamps. The response current of the dot structure was 18.7 microamps.

Claims (4)

1. A surface quantum dot humidity sensor chip, characterized in that it includes a bottom-up GaAs (gallium arsenide) substrate layer (1), an n-type GaAs buffer layer (2), and a buried InGaAs quantum dot layer (3) and the InGaAs surface quantum dot layer (4), the buried InGaAs quantum dot layer (3) is covered with a layer of GaAs, and the buried InGaAs quantum dot layer (3) and the n-type GaAs buffer layer (2) both have a stepped structure at the left and right ends, A vertical first silicon dioxide passivation layer (5) is deposited on the left end step of the buried InGaAs quantum dot layer (3), and the first silicon dioxide passivation layer (5) and the n-type GaAs buffer layer (2) The end face of the second silicon dioxide passivation layer (8) is deposited vertically on the right end step of the buried InGaAs quantum dot layer (3), and the lower right side of the second silicon dioxide passivation layer (8) is at the n A third lateral silicon dioxide passivation layer (7) is deposited on the n-type GaAs buffer layer (2), and an n-type GaAs buffer layer (2) is deposited on the third silicon dioxide passivation layer (7). Connected Au/Ge/Ni alloy lower electrode (10), InGaAs surface quantum dot layer (4) has a lateral fourth silicon dioxide passivation layer connected with the first silicon dioxide passivation layer (5) on the left side layer (6), and an Au/Ge/Ni alloy upper electrode (9) communicating with the InGaAs surface quantum dot layer (4) is deposited on the fourth silicon dioxide passivation layer (6). 2. The surface quantum dot humidity sensor chip according to claim 1, characterized in that: the buried InGaAs quantum dot layer (3) is 1-15 layers. 3. The surface quantum dot humidity sensor chip according to claim 1, characterized in that: the thickness of each buried InGaAs quantum dot layer (3) is not greater than 20nm. 4. The surface quantum dot humidity sensor chip according to claim 1, characterized in that: the chip is circular.