CN116666467A - Band gap adjustable structure and photoelectric conversion device structure - Google Patents

Abstract

The invention discloses a band gap adjustable structure, which comprises a semiconductor substrate and a semiconductor functional layer which are sequentially arranged, wherein the semiconductor functional layer has an in-plane periodic structure, the in-plane periodic structure consists of two structural unit layers with different components or different components, and the components of the structural unit layers are compounds composed of IIIA group elements and VA group elements. The invention also discloses a photoelectric conversion device structure based on the structure. The semiconductor functional layer with the in-plane periodic structure is realized by a molecular beam epitaxy technology, and the distribution of corresponding elements in the plane can be caused to be periodic due to different atom migration, so that the photoluminescence spectrum of the semiconductor functional layer can be shifted, and the working wave band of corresponding materials is expanded. Furthermore, since the periodic structure is along the in-plane direction, light of different angles can be detected and emitted.

Description

A bandgap adjustable structure and photoelectric conversion device structure

technical field

The invention relates to an in-plane periodic structure with adjustable band gap and a photoelectric conversion device structure based on the structure, belonging to the field of semiconductor infrared photoelectric conversion device materials and the field of semiconductor material manufacturing.

Background technique

InP-based photodetectors in the near-infrared band generally use thicker ternary alloys or periodically stack quantum wells along the growth direction as the photoelectric conversion layer. For ternary alloys, when matching with the InP substrate lattice, the content of each element is fixed as follows: In _0.48 Al _0.52 As, In _0.53 Ga _0.47 As, GaAs _0.5 Sb _0.5 , AlAs _0.55 Sb _0.45 , resulting in the working of the material The band is fixed, and changing the working band of the material by changing the composition will introduce problems such as mismatch. Superlattice or multiple quantum wells can better solve the problem of this working band. Through inter-band transition and intra-band transition, the working band of the material can be effectively expanded. The quantum wells formed by these compounds along the growth direction are restricted in the sub-band transition of electrons in the quantum well due to the transition rules. It is necessary to change the angle between the incident light and the quantum well to make the quantum well have obvious inter-subband absorption. The existing devices mainly make the multi-quantum in the device by incident the incident light at a certain oblique angle, or achieve the total internal reflection condition. The well has obvious absorption to the optical signal, which is quite challenging for the processing and optical coupling of small-sized optoelectronic devices.

Contents of the invention

In order to overcome the above technical deficiencies, the present invention provides an adjustable bandgap structure and a photoelectric conversion device structure.

In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

The invention provides a structure with adjustable bandgap, which includes a semiconductor substrate and a semiconductor functional layer arranged in sequence, wherein the semiconductor functional layer has an in-plane periodic structure, and the in-plane periodic structure consists of two different components or structures of different components The composition of the unit layer, the composition of the structural unit layer is a compound composed of IIIA group and VA group elements.

In a preferred embodiment of the invention, the semiconductor functional layer is grown on the semiconductor substrate by epitaxy.

In some embodiments of the present invention, the compound composed of Group IIIA and Group VA elements is a multi-component compound. In a preferred solution of the present invention, the multi-component compound is In _x Ga _1-x As, In _x Al _1-x As, Al _x Ga _1-x As, InAs _x Sb _1-x , GaAs _x Sb _1-x or AlAs _x Sb _1-x .

In some embodiments of the present invention, the thickness of the semiconductor functional layer is 0-1000 nm, and the period length of the in-plane periodic structure is 10-100 nm.

In some embodiments of the present invention, the angle between the in-plane periodic structure and the surface of the semiconductor substrate is 80-100°.

In some embodiments of the present invention, the adjustable bandgap structure also includes a buffer layer, the buffer layer is arranged between the semiconductor substrate and the semiconductor functional layer, and the material of the buffer layer is a wide bandgap ternary material lattice-matched with the semiconductor substrate. Alloy materials.

The present invention also provides a photoelectric conversion device structure, including sequentially setting the bottom electrode, the above-mentioned adjustable bandgap structure, a contact layer and a top electrode, wherein an ohmic structure is formed between the bottom electrode and the semiconductor substrate, and the contact layer and the top electrode Ohmic contact is formed between them.

In some embodiments of the present invention, the contact layer is an artificially doped semiconductor layer, wherein the material of the artificially doped semiconductor layer is In _x Ga _1-x As, In _x Al _1-x As, Al _x Ga _{1 -x} As, InAs _x Sb _1-x , GaAs _x Sb _1-x or AlAs _x Sb _1-x and compounds formed in combination, the doping source of the artificially doped semiconductor layer includes Si, Te, Be and C .

Beneficial effect

The bandgap adjustable structure provided by the present invention has a special in-plane periodic structure, the direction of the periodic arrangement is perpendicular to the growth direction, and the length of the period can be adjusted by the growth temperature. Since the periodic structure is uniformly distributed in the plane , can form a multi-quantum well structure perpendicular to the growth direction. Due to the quantum effect, discrete energy levels will be formed inside the multi-quantum well in the plane. This periodic multi-quantum well structure in the plane satisfies the transition between subbands in the quantum well. Then, the periodic structure in the plane is responsive to the light perpendicular to the surface, which can be used for the infrared optoelectronic device of the inter-subband transition of the vertically incident light detection. At the same time, due to the difference in the migration of group IIIA atoms, the periodic structural units in the in-plane periodic structure will have different components or components and period lengths, which will change the effective bandgap of structures with different in-plane period lengths, This can make the working band of the photoelectric device formed by the in-plane periodic structure adjustable. The present invention can accurately control the growth temperature through molecular beam epitaxy equipment, and control the migration of surface atoms during growth through temperature, so that in-plane periodic structures with different characteristic lengths are formed during the growth process, and the components present periodic distribution in the plane, forming an in-plane periodic structure.

Description of drawings

Fig. 1 is a schematic diagram of the adjustable bandgap structure in the present invention.

Fig. 2 is a schematic structural diagram of a photoelectric conversion device based on an adjustable bandgap structure in the present invention.

Fig. 3 is a cross-sectional transmission electron micrograph of the bandgap tunable structure with an in-plane periodic structure in Example 1 of the present invention.

Fig. 4 is an X-ray reciprocal space scanning result of the bandgap tunable structure with an in-plane periodic structure in Example 1 of the present invention.

Fig. 5 is an 80 K photoluminescence diagram of the bandgap tunable structure with different in-plane period lengths and no in-plane period structure in Example 1 of the present invention.

Fig. 6 is a schematic structural diagram of a photoelectric conversion device having an in-plane periodic structure of InAlAs with different compositions in Example 2 of the present invention.

Implementation

The present invention will be described in further detail below in conjunction with the accompanying drawings.

The present invention provides a structure with adjustable bandgap, as shown in FIG. 1 , which includes a semiconductor substrate 1 and a semiconductor functional layer 2 , wherein the semiconductor functional layer 2 has an in-plane periodic structure. The in-plane periodic structure is composed of structural unit layers 2.1 and 2.2 of different components or compositions, and the components of these structural unit layers are compounds composed of group IIIA and group VA elements. In the present invention, the in-plane periodic structure of the semiconductor functional layer 2 is substantially perpendicular to the surface of the semiconductor substrate 1, and the angle between them is 80-100°.

In the present invention, the semiconductor functional layer can be directly grown on the semiconductor substrate by epitaxy, and the growth temperature can be precisely controlled by the molecular beam epitaxy equipment, thereby controlling the migration of surface atoms during growth, so that different characteristic lengths can be formed during the growth process. In-plane periodic structure, the components present a periodic distribution in the plane, forming a periodic structure in the plane. Preferably, the growth temperature of the semiconductor functional layer is 300-600°C. At the same time, by controlling the rate or beam current ratio of group VA and group IIIA elements, the period length of the in-plane structure can be more precisely regulated.

In the present invention, the compound composed of Group IIIA and Group VA elements constituting the structural unit layer may be a binary compound or a multi-component compound, and its existence form is a random alloy, or a digital alloy (short-period superlattice) in the vertical in-plane direction . Preferably, the compound composed of Group IIIA and Group VA elements constituting the structural unit layer is a multi-component compound, such as In _x Ga _{1- x} As, In _x Al _1-x As, Al _x Ga _1-x As, InAs _x Sb _{1 -x} , GaAs _x Sb _1-x , or AlAs _x Sb _1-x . By adjusting the different proportions of elements in the structural unit layer, the optical bandgap of the semiconductor functional layer 2 can be changed to realize the function of adjusting the response band.

As shown in Figure 1, the thickness a of the semiconductor functional layer 2 is 10-1000 nm. This functional layer is used to absorb light to generate photogenerated carriers. The thickness of the semiconductor functional layer can be changed according to actual application requirements to achieve a suitable quantum efficiency. The period length b (the total thickness of the structural unit layer 2.1 and the structural unit layer 2.2) of the in-plane periodic structure is 10-100 nm. In the present invention, the in-plane period length can be controlled by the growth temperature, and different growth temperatures can drive the surface migration process of atoms to realize the change of the period length and the composition of the modulation region. Different period lengths can be changed due to their quantum confinement , so it has a wide range of tuning effects on the working band of the device.

In the present invention, the adjustable bandgap structure can also include a buffer layer, which is arranged between the semiconductor substrate 1 and the semiconductor functional layer 2, which can further improve the surface flatness, reduce the dislocation density, and provide a good conductive contact layer and other functions. . The material of the buffer layer can be selected from a wide-bandgap ternary alloy material that matches the lattice of the semiconductor substrate. For example, if the semiconductor substrate is InP, the buffer layer can be selected from InAlAs, InGaAs, GaAs, AlAs or a super alloy composed of the above two materials. lattice structure. The buffer layer may be an artificially doped semiconductor layer.

The present invention provides a photoelectric conversion device structure, as shown in Figure 2, which includes a bottom electrode 4 arranged in sequence, a bandgap adjustable structure (semiconductor substrate 1 and a semiconductor functional layer 2 with an in-plane periodic structure), contact Layer 3 and top electrode 5, wherein an ohmic contact is formed between the bottom electrode 4 and the semiconductor substrate 1, and an ohmic contact is formed between the contact layer 3 and the top electrode. The optoelectronic device can realize the detection and light emitting functions of near-infrared to mid-infrared light. Due to the periodic structure in the surface of the semiconductor functional layer 2, the working band can be extended to the near-infrared band. In addition, due to the formation of multiple quantum wells, the transition between sub-bands in the quantum wells can be extended to the mid-infrared band. When near-infrared or mid-infrared light is incident on the surface of the device, the semiconductor functional layer 2 absorbs the light to generate non-equilibrium carriers, and the photogenerated carriers are exported through the upper and lower electrode layers to form a photocurrent to complete the light detection process.

The contact layer 3 is an artificially doped semiconductor layer. For devices with InP as the substrate, the preferred material for the contact layer 3 is In _0.48 Al _0.52 As, In _0.53 Ga _0.47 As, GaAs _0.5 Sb _0.5 , AlAs _0.55 Sb _0.45 or the above-mentioned A multi-component alloy formed of two or more compounds. The artificially doped semiconductor layer can be an n-type or p-type doped semiconductor layer, and the doping source includes Si, Te, Be and C, and the selection of a suitable doping source will make the doped semiconductor layer maintain the crystal quality and surface In the case of flatness, the non-equilibrium carriers generated in the semiconductor functional layer 2 with the in-plane periodic structure can be effectively extracted or introduced into the semiconductor functional layer 2 with the in-plane periodic structure. The doping amount of the doping source is determined according to the electrode contact barrier, but generally not less than 1×10 ¹⁸ cm ^-3 . The selection of the material of the contact layer 3 needs to follow the principle that its band gap is greater than that of the superlattice functional layer and the lattice constant matches the semiconductor substrate. Problems such as the lattice quality of the electrode layer lead to poor performance of subsequent devices processed based on the epitaxial structure. In the present invention, the thickness of each layer in the strain-compensated short-period superlattice photodetection device is not particularly limited, and an appropriate thickness is selected according to actual needs. Specifically, the thickness of the contact layer 3 is 100-1000 nm.

The technical solutions in the present invention will be described below in conjunction with the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of them. In the embodiments, the InAs/AlAs superlattice structure The in-plane periodic structure appears, the in-plane period length is 12 nm and 24 nm, and its photoluminescence result can be obtained from the obvious red-shift behavior. Based on the embodiments of the present invention, all other implementations obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Example 1:

In-plane periodic structure in InP-based InAs/AlAs superlattice films. The specific plan is as follows:

(1) Deoxidize the InP (001) substrate in an arsenic atmosphere for 15 minutes, and the deoxidation temperature is 520-540°C;

(2) Epitaxial buffer layer by molecular beam epitaxy growth method: background vacuum degree is 1×10 ^-7 ~1×10 ^-8 torr, epitaxy InAlAs random alloy semiconductor material at 490°C, the thickness is 100 nm, and the growth rate is 0.9 μm/h;

(3) Epitaxial semiconductor functional layer by molecular beam epitaxy growth method: cool the obtained material to 450-500°C at a cooling rate of 30°C/min, and epitaxially grow a layer with a thickness of 250 nm on the buffer layer by molecular beam epitaxy The InAs/AlAs superlattice controls the migration of surface atoms through the growth temperature to form In _x Al _1-x As in-plane periodic structures with different In components.

Fig. 3 is a cross-sectional scanning transmission electron microscope image of the bandgap tunable structure with an in-plane periodic structure in Example 1 of the present invention. It can be seen from Figure 3 that the in-plane periodic structure runs through the InAs/AlAs superlattice film, and has a good in-plane periodicity, and the in-plane period length is about 24 nm.

Fig. 4 is a reciprocal space scanning diagram of X-ray diffraction of the bandgap tunable structure with an in-plane periodic structure in Example 1 of the present invention. It can be seen from Figure 4 that the in-plane periodic structure has a certain degree of adjustability and good periodicity. Under different growth temperatures, the period length of the in-plane periodic structure has a certain degree of tuning. The In _x Al ₁ grown at 475°C The in-plane periodic structure of _-x As and In _y Al _{1- y} As has an in-plane period of 12 nm, while the in-plane periodic structure of In _x Al _1-x As and In _y Al _1-y As grown at 500 °C The in-plane period of is about 24 nm.

Fig. 5 is a photoluminescence spectrum diagram of the structure with adjustable bandgap in Example 1 of the present invention. It can be seen from FIG. 5 that after the in-plane periodic structure appears in the semiconductor functional layer, its band gap will be reduced. The larger the in-plane period length, the smaller the band gap.

Example 2:

The device structure of the in-plane periodic structure in the InP-based InAs/AlAs superlattice film, the specific scheme is as follows:

(1) Deoxidize the InP (001) substrate in an arsenic atmosphere for 15 minutes, and the deoxidation temperature is 520-540°C;

(2) The doped buffer layer was epitaxially grown by molecular beam epitaxy: the background vacuum was 1×10 ^-7 ~1×10 ^-8 torr, and the InAlAs random alloy semiconductor material was epitaxially grown at 490°C with a thickness of 100 nm. The growth rate is 0.9 μm/h, and the doping sources include Si, Te, Be and C;

(3) Epitaxial InAlAs semiconductor functional layer by molecular beam epitaxy growth method: cool the obtained material to 450-500°C at a cooling rate of 30°C/min, and epitaxially grow a thickness of 250 nm on the buffer layer by molecular beam epitaxy The InAlAs thin film, the surface atom migration is controlled by the growth temperature, so that the in-plane periodic structure of In _x Al _1-x As and In _y Al _1-y As is formed;

(4) epitaxially doping the InAlAs contact layer by molecular beam epitaxy: using molecular beam epitaxy to epitaxy an InAlAs film with a thickness of 500 nm on the semiconductor functional layer, and the doping sources include Si, Te, Be and C;

(5) Evaporating a metal electrode layer on the front and back of the above-mentioned epitaxial growth structure by means of evaporation to form an ohmic contact with the corresponding substrate and the upper doped contact layer.

Fig. 6 is a schematic diagram of a device structure with a lateral periodic structure grown on an InP base in Example 2 of the present invention.

Claims (9)

1. The band gap adjustable structure is characterized by comprising a semiconductor substrate and a semiconductor functional layer which are sequentially arranged, wherein the semiconductor functional layer is provided with an in-plane periodic structure, the in-plane periodic structure is composed of two structural unit layers with different components or different components, and the components of the structural unit layers are compounds composed of IIIA group elements and VA group elements.

2. The band gap tunable structure of claim 1, wherein the semiconductor functional layer is grown on the semiconductor substrate by an epitaxial process.

3. The band gap tunable structure of claim 1, wherein the compound of group IIIA and group VA elements is a multi-compound.

4. A bandgap tunable structure according to claim 3, wherein said polynary compound is In _x Ga _1-x As、In _x Al _1-x As、Al _x Ga _1-x As、InAs _x Sb _1-x 、GaAs _x Sb _1-x Or AlAs _x Sb _1-x 。

5. The band gap tunable structure of claim 1, wherein the semiconductor functional layer has a thickness of 10-1000 a nm a period length of the in-plane periodic structure of 10-100 a nm a.

6. The band gap tunable structure of claim 1, wherein the in-plane periodic structure is at an angle of 80-100 ° to the semiconductor substrate surface.

7. The bandgap tunable structure of claim 1, further comprising a buffer layer disposed between said semiconductor substrate and said semiconductor functional layer, said buffer layer being of a wide bandgap ternary alloy material lattice matched to said semiconductor substrate.

8. A photoelectric conversion device structure, comprising a bottom electrode, the band gap adjustable structure of any one of claims 1 to 7, a contact layer, and a top electrode, which are sequentially disposed, wherein ohmic contact is formed between the bottom electrode and the semiconductor substrate, and ohmic contact is formed between the contact layer and the top electrode.

9. The structure of claim 8, wherein the contact layer is a human doped semiconductor layer, wherein a material of the human doped semiconductor layer is In _x Ga _1-x As、In _x Al _1-x As、Al _x Ga _1-x As、InAs _x Sb _1-x 、GaAs _x Sb _1-x Or AlAs _x Sb _1-x And a compound formed by combination, wherein the doping source of the artificially doped semiconductor layer comprises Si, te, be and C.