JP2699838B2 - Infrared detector and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor having a narrow bandgap,
In particular the infrared detector and its using a compound semiconductor containing Hg
And a method for producing the same.

[0002]

2. Description of the Related Art It is generally known that an infrared detector using a semiconductor having a narrow band gap has high sensitivity. Among them, a photovoltaic element having a pn junction in a detection portion is very effective for an infrared imaging apparatus having a configuration in which single elements are two-dimensionally arranged.

A typical example of the photovoltaic infrared detector using HgCdTe will be briefly described with reference to FIG. H is formed on the CdTe substrate 1 using the MBE method.
The gCdTe layer is epitaxially grown, and a p-HgCdTe layer 3 composed of Hg vacancies is formed by heat treatment in an Hg atmosphere. Thereafter, ion implantation is performed partially by performing ion implantation using a resist mask, and heat treatment is performed to diffuse Hg between lattices to the back of the crystal in order to avoid deterioration in characteristics due to ion implantation damage. n
^- forming a -HgCdTe region 5, to move the pn junction interface 8 to the damage free areas. Finally, a protective film 6 and an electrode 7 are formed to complete the device.

The incident infrared light is absorbed by the p-HgCdTe layer 3 and the n ⁻ -HgCdTe region 5 and diffuses as electrons or holes, is electrically separated at the pn junction, and is used as a signal at the electrode 7 (p-side). The electrodes are omitted here).

[0005]

However, such an infrared detector has the following disadvantages.

As described above, the ion implantation method is used for forming the pn-type junction, which is the most advantageous method in view of controllability and simplicity. Is a general method of performing heat treatment. By this heat treatment, Hg between lattices generated by ion implantation diffuses through Hg vacancies in the p-HgCdTe layer 3 to form a pn junction in a region where ion implantation is not damaged, but the diffusion is relatively fast. In addition, it is difficult to sufficiently control the diffusion front, that is, the pn junction interface 8, because it largely depends on the number of Hg vacancies. In particular, when a thin HgCdTe layer having a thickness of about 10 to 15 μm is used as an epitaxial crystal, the pn junction may be moved to the vicinity of the interface with the substrate having a large lattice distortion due to the heat treatment.
There is also a possibility that characteristic deterioration such as an increase in dark current may be caused.

[0007] It is an object of the present invention to provide an infrared detector which eliminates these disadvantages and a method of manufacturing the same.

[0008]

Means for Solving the Problems] photovoltaic infrared detector of the present invention, the infrared detector using a compound semiconductor containing Hg, have a first compound semiconductor layer doped with p-type dopant on the substrate And the first compound semiconductor
Has a second compound semiconductor layer of p-type which is an acceptor of Hg vacancies on the layer, and the second compound semiconductor layer, n-type regions as a donor of Hg between grating is formed It is characterized by the following.

[0009]

The infrared detection device in which a plurality of compound semiconductor layer to the action substrate, large Hg ₁ x values on CdTe substrate conventionally _{- x} Cd _x Te buffer layer and the x value smaller Hg _{1 - x} Cd _x A diode in which a Te layer is laminated has already been proposed (Japanese Patent Laid-Open No. 1-233777, etc.). This is an apparatus aimed at selectively reducing the carrier concentration only in a portion where a diode is formed and reducing crosstalk between diodes (pixels). In such a configuration, it was impossible to control the diffusion of Hg, and the object of the present invention could not be achieved.

On the other hand, in the infrared detector of the present invention, a layer doped with a p-type dopant such as As is provided near the interface with the substrate, and a p-type layer having Hg vacancies as an acceptor is provided thereon. Using a type HgCdTe crystal, a normal process including formation of a pn junction diode by ion implantation, heat treatment after implantation, and the like are performed. The p-type HgC of the above two-layer structure
Since the dTe crystal is used, Hg between lattices diffused through Hg vacancies due to the heat treatment stops at the layer doped with the p-type dopant having almost no Hg vacancies. Therefore, the pn junction position does not reach the vicinity of the interface with the substrate where a large amount of lattice distortion is present, and deterioration of diode characteristics such as an increase in dark current due to the pn junction position is not observed.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention. The manufacturing method of the present invention in which a photodiode is formed on two layers of p-type HgCdTe crystals having different types of acceptors will be briefly described.

An As-doped p-HgCdTe layer 2 is formed on a CdTe substrate 1 by a 5 μm, non-doped HgCd
Te is grown by MBE in order of 5 μm, Hg vacancies are formed in non-doped HgCdTe by p-annealing in an Hg atmosphere, and the p-HgCdTe layer 3 is formed by the Hg vacancies. Thereafter, boron (B) is partially ion-implanted through a mask of about 50 μmφ to form a pn junction.
The ion implantation energy may be about 150 keV. At this time, the activated B and Hg between the lattices generated by the ion implantation serve as the n-type donor. Pn from the ion implantation damage region near the ion implantation region 4
Heat treatment is performed at 150 to 200 ° C. for about 1 hour to keep the junction away. At this time, Hg between lattices is p-HgCdTe
Diffused through the Hg vacancies in layer 3 to form n ⁻ -HgCdTe
While the region 5 is formed, the position of the pn junction is moved outward as a whole, but the diffusion in the depth direction is made of As-doped p-type.
It stops at the interface with the HgCdTe layer 2. This is the interstitial H
This is because there is almost no Hg vacancy in the p-HgCdTe layer 2 that assists in the diffusion of g. Further, this interface is formed by a series of growths, and there is no deviation of the lattice constant, so that the interface level and the trap level caused by lattice defects are very small. Thereafter, a protective film 6 and an electrode 7 are formed to complete the device.

Next, the operation will be briefly described. The incident infrared light is the As-doped p-HgCdTe layer 2, Hg
P-HgCdTe layer 3 and n ^-- HgCdT by vacancies
It is absorbed in the e-region 5, diffuses as electrons or holes, is electrically separated at the pn junction, and is output as a signal from the electrode 7 (the p-side electrode is omitted here).
At this time, as described above, in the structure of the present invention, since a lattice defect near the pn junction which causes dark current is very small, a diode having excellent characteristics can be obtained.

As described above, according to the present invention, a pn junction can be formed with good controllability away from the vicinity of the interface with the CdTe substrate having many lattice defects such as strains. Hg with good characteristics without reduction
A CdTe diode can be manufactured with good reproducibility.

In this embodiment, the case where a p-HgCdTe layer is used as a compound semiconductor having a narrow band gap is shown. However, if the pn junction formation mechanism involving the diffusion of Hg is equivalent, the material and the process conditions are the same. It is not limited to.

[0017]

As described above in detail, the present invention provides a HgCdTe diode having good characteristics without a decrease in the yield of the device due to the uncertainty of the heat treatment, and sufficiently contributes to the high performance of the infrared detector. Things. In other words,
In the light, interface with CdTe substrate with many lattice defects such as strain
A pn junction can be formed with good controllability away from the vicinity,
As a result, the case near the pn junction causing dark current
Interface states and trap states caused by
Diodes with few and good characteristics can be obtained. Plus heat
Good device yield without reduction in process uncertainty
Producing HgCdTe Diodes with High Reproducibility
Can be.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an HgCdTe diode according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a conventional HgCdTe diode.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 CdTe substrate 2 As-doped p-HgCdTe layer 3 p-HgCdTe layer with Hg vacancies 4 Ion-implanted region 5 n ⁻ -HgCdTe region 6 Protective film 7 Electrode 8 pn junction interface

Claims (2)

(57) [Claims] 1. A infrared detector using a compound semiconductor containing Hg, comprises a first compound semiconductor layer doped with p-type dopant on the substrate, wherein the first compound semiconductor
A p-type second compound semiconductor layer having Hg vacancies as an acceptor on the body layer , and the second compound semiconductor layer
A photovoltaic infrared detector in which an n-type region having Hg between lattices as a donor is formed. (2) P-type dopant near the interface with the substrate
Ping to form a first compound semiconductor layer;
Non-doped compound semiconductor layer on one compound semiconductor layer
Hg vacancies are formed by performing p-type annealing
Forming a p-type second compound layer as a ceptor
And heat treatment after ion implantation.
Forming a pn junction diode in the second compound layer
2. The infrared ray according to claim 1, wherein the infrared ray comprises:
Manufacturing method of detector.