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Method of selective post-growth tuning of an optical bandgap of a semi-conductor heterostructure and products produced thereof

a semi-conductor heterostructure and optical bandgap technology, applied in the direction of laser cooling arrangement, laser construction details, lasers, etc., can solve the problems of deterioration or complete death of device performance, and ion-implantation generation of point defects, so as to improve stability and reproducibility

Inactive Publication Date: 2007-04-26
AGENCY FOR SCI TECH & RES
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

This approach enables simple, effective, and reproducible control of optical bandgaps, allowing for the creation of heterostructures with selectively tuned regions, enhancing the integration of opto-electronic and photonic devices by minimizing device performance degradation and improving spatial selectivity.

Problems solved by technology

This method suffers from several drawbacks.
The presence of doping impurities changes conductivity and conductive type, which either deteriorates or completely kills the device performance.
Introduction of neutral impurities like F and B by ion-implantation generates traps and residual damages, which also deteriorate the device performance.
Ion-implantation generates point defects, such as vacancies in places remote from or over an active region.
A method for QW intermixing by implanting ions directly into an active region and then subjecting the structure to thermal annealing suffers from the fact that a high temperature post-annealing may not fully recover from crystal damages caused by ion-implantation and may introduce inhomogeneous QW intermixing.
A large dose of ion-implantation required for a large post-growth tuning often degrades the quality of the heterostructure.
IFVEI as a function of annealing conditions has been well described in the prior art, but the difficulty in spatial selection of IFVEI still remains, particularly in the case where more than two different optical bandgaps are needed in close proximity on a wafer.
This method suffers from a drawback that in order to allow uniform intermixing at a QW depth by overlapping vacancy diffusion fronts, the dimension of SrF2 masks has to be smaller than or comparable to diffusion lengths of point defects.
Moreover, a SrF2 mask also induces damages and may crack due to thermal stress at an elevated post-growth annealing temperature.
The method is difficult to use under manufacturing conditions, and in giving reproducible results.

Method used

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  • Method of selective post-growth tuning of an optical bandgap of a semi-conductor heterostructure and products produced thereof

Examples

Experimental program
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example 1

[0038] An AlGaAs / GaAs quantum well heterostructure comprising several alternating AlGaAs and GaAs layers each about tens to hundreds of Angstroms thick was grown on a GaAs substrate. An Al interlayer having thickness varying from 0 Å to 600 Å was evaporated on the top-surface of the heterostructure, coated with a dielectric layer of silica and followed by a thermal annealing at 850° C. for 20 minutes in the forming gas ambience. No oxide layer was provided. As shown in FIG. 6, post-growth tuning was affected by adding an Al interlayer between dielectric layer and heterostructure. The degree of tuning varied according to the thickness of the Al interlayer, but does not display a linear dependence due to the absence of the oxide layer.

example 2

[0039] The same heterostructure as in Example 1 was used, but the Al interlayers were deposited on an oxide layer formed on the top surface of the heterostructure. The oxide layer was formed by flowing water-saturated oxygen gas over the structure at 500° C. for 40 minutes. The thickness of oxide layer was about 150 Å. As shown in FIG. 7, post-growth tuning depends linearly on the thickness of an Al interlayer. Comparing with FIG. 6, an oxide layer significantly improves reliability of post-growth tuning. Post-growth tuning can therefore be simply and predictably controlled by the thickness of an Al interlayer.

example 3

[0040] An InGaAs / GaAs quantum well heterostructure comprising several alternating InGaAs and GaAs layers each about tens to hundreds of Angstroms thick was grown on a GaAs substrate. An Al interlayer having thickness varying from 0 Å to 600 Å was evaporated onto an oxide layer formed on the top-surface of the heterostructure, and then coated with a dielectric layer of silica, finally followed by a thermal annealing process. The oxidation and thermal annealing conditions are the same as that of Example 2. The thickness of oxide layer was about 150 Å. The close circles in FIG. 8 show that post-growth tuning in this embodiment depends non-linearly on the thickness of an Al interlayer.

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Abstract

A method of controlling the degree of IFVEI for post-growth tuning of an optical bandgap of a semiconductor heterostructure. The resultant layer structure may contain a semi-conductor heterostructure with one or more regions with selectively modified bandgap. According to one aspect of the invention, a metal interlayer is deposited between the heterostructure and a dielectric layer such as silica. According to another aspect of the invention, an oxidized surface is provided between a dielectric layer and the heterostructure. The presence of the oxide layer improves stability and reproducibility in the post-annealing process. In a further aspect, the oxide layer may be provided between the interlayer and the heterostructure. In one embodiment of the invention, a photoresist mask with a specific pattern is deposited on the surface of the heterostructure so that the interlayer is deposited in an unmasked region whereon post-growth tuning results. In another embodiment, multiple photolithography is performed to deposit interlayers of varying thickness and / or regions on the heterostructure, followed by thermal post-annealing of the dielectric layer. This method produces heterostructures with optical bandgaps having selectively tuned regions.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application is a divisional application of U.S. patent application Ser. No. 09 / 423,401 filed on Nov. 5, 1999.FIELD OF THE INVENTION [0002] The present invention is related to semi-conductor heterostructures with quantum well, multiple quantum well, superlattice or quantum dot structures. In particular, the present invention is related to heterostructures of III-IV compound semiconductors, and the method of selective post-growth tuning of an optical bandgap within the heterostructure. BACKGROUND OF THE INVENTION [0003] Working wavelength of photonic devices, such as semiconductor lasers and modulators, is determined by an optical bandgap of a semiconductor heterostructure having a quantum well structure, a multiple quantum well structure, a superlattice structure or a quantum dot structure. Other opto-electronic components, such as waveguides and optical interconnects, need to operate at an optical frequency that is non-resonant with...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01S5/00H01L21/18H01L21/22H01L21/388H01L33/00
CPCH01L21/182H01L21/388H01L33/0095H01S5/4087
Inventor LI, GANGCHUA, SOO JIN
Owner AGENCY FOR SCI TECH & RES