RU205312U1 - PHOTOELECTRIC CONVERTER BASED ON InP - Google Patents

Abstract

The utility model relates to semiconductor technology, namely to photoelectric converters (PECs) based on indium phosphide (InP), illuminated from the side of the substrate, and can be used to convert light energy, in particular laser radiation, into electrical energy. The photovoltaic converter contains an n-type InP substrate, on which a buffer layer of n-type InP, an active region of undoped InGaAs or InGaAsP, an upper layer of p-type InP, a contact layer of p-type InAsP with a thickness of ( 100-300) nm, n - contact deposited on the substrate, p-contact 6, deposited on the subcontact layer. The photovoltaic converter has a reduced p-type contact resistance. 1 wp f-ly, 2 dwg

Description

The present utility model relates to semiconductor technology, namely to photoelectric converters (PECs) based on indium phosphide (InP), illuminated from the side of the substrate, and can be used to convert light energy, in particular laser radiation, into electrical energy.

One of the reasons for energy loss in semiconductor devices, in particular in photovoltaic converters, is the loss on the resistance of the contacts. Reducing the contact resistance is an important problem for any power devices, for example, for high-power laser photodetectors. In devices based on indium phosphide (InP), there is a problem of obtaining ohmic contacts to InP. InP p-type conductivity is characterized by high resistivity and low charge mobility, which is why obtaining ohmic contacts with low resistance to it presents certain difficulties.

Known photodiode based on InP (see KR101738939, IPC H01L 31/0224, H01L 31/0306, publ. 23.05.2017), which consists of an InP substrate, an InGaAs etching stop layer, an n-InP contact layer, an active layer made of undoped InGaAs, undoped InP layer, antireflection coating and electrical contacts. In this case, during the formation of the structure in the InP layer, meshes are made in the form of a circle etched to the depth of the covering layer and a ring etched to a depth slightly greater than that of the covering layer for further formation of the activation zone and protective ring. Zn: SOG is applied to the etched meshes. In this case, in order to avoid doping the front surface of the diode, it is preliminarily covered with a layer of SiO ₂ or Si _x N _y . After applying Zn: SOG, electrical contacts are made on its surface.

The disadvantage of the known photodiode is the difficulty of obtaining an ohmic contact at the Zn-InGaAs interface.

A known PVC based on InP (see CN202405297, IPC H01L 31/105, H01L 31/0224, H01S 5/026, publ. 29.08.2012), including a substrate of n-type InP, a buffer layer of n-InP, absorbing an undoped InGaAs layer, a p-type InP layer and a p-type InGaAs contact layer to obtain ohmic contacts. The contact to the p-type layer was obtained by sputtering titanium, platinum and gold in such a mode that the contact covered the entire p-region above the diffusion pn-junction.

The disadvantage of the known PVC is the use of a layer of InGaAs, which has a significantly high resistance, as a contact layer to contacts of p-type conductivity.

Known FEP based on InP (see EP0404987, IPC H01L 31/0224, H01L 31/105, publ. 02.01.1991), which coincides with the present technical solution for the greatest number of essential features and taken as a prototype. The prototype PVC includes a substrate of n-type InP, a buffer layer of n-InP, an active region of n- and p-InGaAs, a p-type subcontact layer of InGaAs or InGaAsP, n- and p-contacts deposited, respectively on the substrate and on the intermediate layer, and a layer of p-type InP deposited outside the p-contact.

The disadvantage of the known photoconverter-prototype is that the use of a p-type conductivity contact layer from InGaAs or InGaAsP to contacts does not provide a small resistance for a p-type conductivity contact.

The objective of this technical solution was to develop a photoelectric converter based on InP, which would have a minimum contact resistance of p-type conductivity.

The problem is solved by the fact that the photovoltaic converter includes an n-type InP substrate, an n-type InP buffer layer, an active region of undoped InGaAs, an upper p-type InP layer, a p-type InAsP contact layer, n- and p - contacts applied to the substrate and to the contact layer, respectively. New in the present utility model is the implementation of a p-type InAsP subcontact layer with a thickness of (100-300) nm.

In a photovoltaic converter, the subcontact layer can be made of InAs _0.98 P _0.02 , which provides the lowest p-type contact resistance.

The thickness (100-300) nm of the contact layer is due to the fact that when the thickness of the contact layer is less than 100 nm, when contacts are fused, the interaction of contact metallization and the underlying layers is possible, and at a thickness of more than 300 nm, the layer can begin to have a significant effect on the characteristics of the device. including the displacement of the space charge region.

This FEP is illustrated by a drawing, where:

figure 1 schematically shows a side view in section on the FEP;

figure 2 shows a top view of the FEP.

The present PVC (see Fig. 1, Fig. 2) contains a substrate 1 of n-type InP, on which a buffer layer 2 of n-type InP is formed, an active region 3 of undoped InGaAs or InGaAsP, an upper layer 4 of InP p-type conductivity, contact layer 7 made of p-type InAsP with a thickness of (100-300) nm, n - contact 5, deposited on the substrate 1, p-contact 6, deposited on the contact layer 7.

On two InP (100) substrates doped with Sn with a concentration of n = 3⋅10 ¹⁸ cm ^-3 , the structures of the prototype PVC and the real PVC were grown by the method of gas-phase epitaxy from organometallic compounds (MOCVE). The structures differed in the composition of the contact layer: in the prototype, a p-type InGaAs contact layer was used, and in the present PVC, a p-type InAsP contact layer was used. The subcontact layers were doped with Zn with a concentration of p = 1⋅10 ¹⁸ cm ^-3 and had a thickness of 200 nm. AgMn / Ni / Au contacts with layer thicknesses of 800/600/1000 A, respectively, were applied to the structures obtained through a mask. Then the contacts were fused at a temperature of 380 ° C in a nitrogen atmosphere for 30 seconds. The specific contact resistances were measured by the transmission line method. As a result of measurements, it was obtained that the resistivity of contacts in the prototype PVC was 3.9⋅10 ^{-3 Ohm⋅cm 2} , and the resistivity of contacts in this PVT was 4⋅10 ^{-4 Ohm⋅cm 2} .

Claims (2)

1. A photovoltaic converter including an n-type InP substrate, an n-type InP buffer layer, an InGaAs or InGaAsP active region, a p-type InP top layer and a p-type InAsP contact layer, n- and p - contacts deposited on the substrate and on the contact layer, respectively, characterized in that the contact layer is made of p-type InAsP with a thickness of (100-300) nm. 2. The photoelectric converter according to claim 1, characterized in that the contact layer is made of InAs _0.98 P _0.02 .

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