JPS59161083A - Photo-diode - Google Patents

Abstract

PURPOSE:To enable a response at high speed forming band width of 50GHz or more by constituting a photo-diode by a substrate, a conductive layer, an active layer shaped on the conductive layer, a light-transmitting barrier formed on the active layer and an ohmic contact section, which is formed on the conductive layer and having a common surface with the active layer. CONSTITUTION:The insides of a substrate, a conductive layer 5 and an active layer 9 and a section not protected by a gold mask 10 are damaged by protons. As a proton bombardment, a region 21 is brought to a non-conductive state, and only the lower section of the gold mask 10 remains as an active region. The gold mask 10 is removed, the active layer 9 is etched to a desired shape, and an ohmic contact section 7 is deposited on the conductive layer 5. A light-transmitting barrier layer 11 is deposited on the active layer 9. The active layer 9 is shaped through chemical etching and ion cutting. Consequently, there is the active layer 9 only in the lower section of the barrier layer 11. An insulating layer 13 is deposited on the barrier layer 11, the layer 11 is protected so as not to generate flaws, etc., and the reflection of beams is minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photodiode with high-speed response.

Photodiodes are used in fiber optic communication systems, time domain reflectometers, etc. to convert light into electrical signals. Conventionally, the response speed required for a photodiode was slow, and a photodiode with a vertical mesa structure was sufficient.

However, when high-speed response is required, a photodiode with the above structure, that is, a photodiode having an anode on one side of the chip and a cathode on the other side,
The vertical mesa structure photodiode has parasitic capacitance and parasitic inductance, and therefore has a slow response speed (and is not suitable for devices used in the frequency range of the GHz order).

According to the present invention, it is possible to provide a 7-key barrier photodiode that has a bandwidth exceeding 50 GHz and is capable of high-speed response.

The photodiode of the present invention has a planar structure in which the anode and cathode terminals are formed on the same plane. By adopting the above structure, most of the parasitic capacitance within the mesa structure can be removed. active region
is provided on a semi-insulating substrate, and a transparent Schottky barrier or heterojunction is provided between the active region -F
will be established in An optical diode is mesa-etched into the conductive layer to increase the bandwidth by reducing the edge. A beam lead is provided at the anode and cathode junction to reduce series inductance.

In addition, an integrated gallium arsenide MES)'ET device is
Used as a high speed Schottky barrier photodiode as part of a high speed single chip phototransistor without bonding wires to couple between the MESFET and the photodiode.

The present invention will be explained below using examples.

FIG. 1 is a perspective view of a photodiode of the present invention.

2N to 2E are diagrams showing the manufacturing process of the photodiode of the present invention, and are sectional views taken along line A-4 in FIG. 1.

In FIG. 1 and FIGS. 2A to 2E, the substrate 3 has external dimensions of approximately 3 (1,48
2ml1l)X30.48Xl 0-3crrL(12
ml) and the thickness is approximately 7.62 x 10-3 cm (3
mil ) to about 12.7 X 10-3C0-3CI
The substrate 3 is made of semi-insulating GaAs with a doping concentration of 5 x 1018/
A 0.4 pm thick electrically conductive layer 5 of n"GaAs of cm3 is deposited. The electrically conductive layer 5 has a doping concentration of 5x
It is covered with an active layer 9 having a thickness of 0.4 μm and made of n-GaJs of about 1O15/c1rL3.

In FIG. 2N, the proton bombardment stage is shown, in which in the substrate 3, the conductive layer 5 and the active layer 9,
As a result of proton bombardment, where the portion not protected by the gold mask 10 is damaged by protons, the region 21 becomes non-conductive and only the lower part of the gold mask IO remains as an active region.

FIG. 2B shows the view after the gold mask lO has been removed, the active layer 9 has been etched into the desired shape and the ohmic contacts 7 have been deposited on the conductive layer 5. In FIG. 2C, a light-transmissive barrier layer 11 has been deposited on the active layer 9-H. The barrier layer 11 is made of, for example, 100A aluminum and constitutes a Schottky barrier diode. Further, the barrier layer 11 has an aluminum concentration of about 30%.
In this case, it can also be constructed of a heterojunction layer of 4000 A thick gallium-aluminum arsenide compound or the like that is transparent in a wavelength band around 845 nm. In FIG. 2D, active layer 9 is formed into the shape shown in FIG. 1 by chemical etching and ion cutting. As a result, the active layer 9 exists only under the barrier layer 11. In FIG. Minimize reflections. The junction between the active layer 9 and the barrier layer 11 under the insulating layer 13 is a diode 2 with a square size of 5 μm.
The diode 27 forming the diode 7 is activated by protons passing through the insulating layer 13. A meb-etched region 23 with a width of 2 μm is provided around the diode 27 .

By providing the region 23, the outer edge can be reduced and the band width can be increased. In FIG. 2E, insulating layer 1
3 depicts only the diode 27 in the same way, but the area 23 and the ohmic contact portion 7 can also be shown in the same way.

FIG. 3 is a plan view of the photodiode 41 of the present invention.
Beam leads 37, 39 are provided at the ends. To construct photodiode 41, photodiode l shown in FIGS. 1 and 2A-26 is used.

A metal layer 31 is deposited on the barrier layer 11 to reduce the series resistance. Gold pads 33 , 35 are deposited on the metal layer 31 and the ohmic contact 7 . The Zetsudo layer 13 and the gold bands 33 and 35 are masked and photo-protective.
The remaining portions of diode 41 may be coated with polyimide. Beam leads 37, 39 are deposited and photodiode 41 is etched to the desired shape and size. Beam lead 37 functions as an anode terminal to photodiode 41, and beam lead 39 functions as a cathode terminal.

Figure 4 shows MB5J using the photodiode of the present invention.
'E,T is a perspective view of a photodiode.

MESF'ET photodiode 61 is an integration of photodiode 1 and MESF'ET 53 on a common Gaps substrate. MESFIE
T53 has drain 55, gate 57 and source 59
and is formed using well-known techniques (19
June 1976 All June Transactions on Microwave Theory and Chikunya Shoes Vol.1. M
TT-24, No. 6, 279 Hessi). By forming it with a low doping concentration, photodiode l can be operated at bias levels as low as tV. This is approximately the same as the operating range of the transistor. Various matching circuits can be used between photodiode l and MESF12T53. FIG. 5 shows a circuit configuration when using the photodiode of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a photodiode of the present invention. 2N to 2E are diagrams showing the manufacturing process of the photodiode of the present invention. FIG. 3 is a plan view of the photodiode of the present invention. Figure 4 shows an ME using an uninvented photodiode.
FIG. 2 is a perspective view of an ESFET photodiode. FIG. 5 is a circuit diagram when using the photodiode of the present invention. 1: Photo-diode 3: Substrate 5: Conductive layer 7 Two-ohm contact portion 9: Active layer 11: Barrier layer 13: Insulating layer

Claims (1)

[Claims] a substrate, a conductive layer provided on the substrate, an active layer provided on the conductive layer, a light-transmitting barrier provided on the active layer, and a conductive layer provided on the conductive layer; A photodiode comprising said active layer and a coplanar ohmic contact.