Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – Active layer of indirect band gap semiconductor
Patent
1997-12-05
1999-11-30
Jackson, Jr., Jerome
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
Active layer of indirect band gap semiconductor
257 79, 257 96, H01L 3300
Patent
active
059947209
DESCRIPTION:
BRIEF SUMMARY
INTRODUCTLON AND BACKGROUND
This invention relates to indirect bandgap semiconductor technology (such as silicon integrated circuit technology and more particularly to discrete and monolothically integrated opto-electronic devices produced from these semiconductor materials.
The present known solid state light emitting devices comprise complex structures of composite direct bandgap semiconductor material from the Group II, III, V and VI elements, for example gallium-arsenide-phosphide. These devices are expensive, are not operationally compatible with the signal processing circuitry found on silicon integrated circuits and cannot monclithically be integrated with the existing silicon integrated circuit technology.
OBJECT OF THE INVENTION
It is an object of the present invention to provide an optoelectronic device and a method of producing same with which the applicant believes the aforementioned disadvantages may at least be alleviated.
SUMMARY OF THE INVENTION
According to the invention there is provided an optoelectronic device comprising a visibly exposed region of a suitable material adjacent a surface region of a layer of a doped indirect bandgap semiconductor material, to provide a first junction region close to the surface region; the first junction region, in use, being reverse biased, to cause the device to act as an optoelectronic device, either by emitting light outwardly beyond the surface region or to detect incident photons impinging on the device from beyond the surface region.
In a first form the visibly exposed region may comprise a highly, but oppositely doped region of the indirect bandgap semiconductor material and said layer comprises an epitaxial layer; the highly doped region being embedded in the surface region of the epitaxial layer.
The indirect bandgap material may be silicon or any other suitable indirect bandgap material.
The said highly doped region may comprise n.sup.- doped silicon and the epitaxial layer p type silicon. It will be appreciated that complementary doping may be utilized to provide a complementary p.sup.- in n-based silicon structure.
A guard ring structure of lighter doping than the said highly doped region may be provided to circumscribe the said highly doped region and to extend deeper into the epitaxial layer than the highly doped region.
In a first embodiment of the first form the highly doped region may be planar and continuous. It may typically be 0.3 .mu.m deep, so that the first junction region is located in the order of 0.3 .mu.m below the surface region of the device.
The defect state density in the said highly doped region is preferably much higher than the defect state density in the epitaxial layer, which layer preferably is substantially defect free. The detect density in the highly doped region is preferably uniformly distributed.
The said highly doped region may be imbedded in a base layer of the same, but higher doping concentration as the epitaxial layer to reduce the avalanche breakdowm voltage of the device.
In another embodiment the said highly doped region may be in the form or shape of a grid embedded in the epitaxial layer so that the first junction region periodically extends up to the surface region of the device, thereby to increase the surface area of the first junction region and to decrease the distance between the first junction region and the surface region.
The grid-like highly doped region may define square regions through which the epitaxial layer or base layer, as the case may be, extends.
In yet another embodiment the said highly doped region may be in the form of a plurality of concentric rings embedded towards the surface region of the epitaxial layer. The concentric rings are inter-connected by resistive doped regions of the same dopant type. A highly, but oppositely doped current feed region nay be provided at a centre of the concentric rings, to be in electrical contact with the epitaxial layer and base layer.
Control gates may be provided between the said current feed region and an adjacent ring as well as betw
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Yeh, et al., Light Emission of PN Junction, IBM Technical Disclosure Bulletin, vol. 9, No. 7, p. 919, Dec. 1966.
Kramer et al., Industrial CMOS Technology for the Integration of Optical Metrology Systems (Photo-ASICs), Sensors and Actuators A, 34, pp. 21-29, 1992.
Kramer et al., Light-Emitting Devices in Industrial CMOS Technology, Sensors and Actuators A, 37-38, pp. 527-532, 1993.
Aharoni Herzl
DuPlessis Monuko
Snyman Lukas W.
Baumeister B W
Jackson, Jr. Jerome
Spaeth Frederick A.
University of Pretoria
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