High quality metamorphic graded buffers with lattice-constants intermediate to GaAs an InP for device applications

We have investigated the use of a continuous, linear grading scheme for compositionally-graded metamorphic InxGal-As buffers on GaAs, which can be used as virtual substrates for optical emitters operating at wavelengths > 1.2 gm. Such virtual substrates will allow access to new materials that can be used for designing optical and electronic devices with superior characteristics and performances compared with conventional devices that are grown lattice-matched on standard substrates such as GaAs and InP. In addition, the principles behind such graded buffers can be used to bridge different lattice-constants, which can be a pathway to future integration of previously distinct classes of devices that have been defined by the lattice-constant on which they were built (e.g. Si-based, GaAs-based, InP-based etc.). Graded buffers with threading dislocation densities (TDD) < 9.5 x 104 cm-2, at a final composition of x = 0.346 were obtained, representing the lowest value ever achieved at or around this composition. Photoluminescence (PL) measurements were carried out on InGaAs quantum wells (QWs) that were re-grown on these buffers, and high luminescence efficiency was observed in the 1.2-1.5 tm wavelength range. Ridge waveguide QW-separate confinement heterostructure lasers and heterojunction bipolar transistors (HBTs) were also grown on the graded buffers to demonstrate their applicability for device applications. Pulsed threshold current densities of 262 Ac2 at room temperature were obtained for 2 mm long strained-InGaAs QW emitting at 1320 nm, with peak output powers up to 40 mW. Preliminary tests on the unoptimized HBTs revealed that they operate with dc current gains of up to 13. A new class of graded buffers using all-binary III-V semiconductors has also been demonstrated. Thin constituent layers of GaAs and InP are combined such that they act in a mechanically-similar fashion as a random alloy.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2009

Author dc:creator

• Lee, Kenneth Eng Kian

Advisor dc:contributor.advisor

• Eugene A. Fitzgerald.

• Electrical Engineering and Computer Science.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/47779

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/47779