Massachusetts Institute of Technology

George W Turner

John C Fan

Jack P Salerno

Bor-Yeu Tsaur

Anish K Goyal

Hong K Choi

Stephen J Eglash

Adrian J Isles

Bettina A Nechay

A semiconductor laser operating in the mid-infrared region is described. In one particular embodiment, the semiconductor laser is provided having first and second cladding layers consisting essentially of GaSb that surround an active core, wherein the index of refraction of the first and second cladding layers is less than but close to the index of refraction of active core. The semiconductor laser in accordance with this invention has a low divergence angle with a high power efficiency. In an alternate embodiment, the semiconductor laser is provided having first and second cladding layers consisting essentially of Al Ga As Sb that surround the active core with an aluminum mole fraction between 0 and 25 percent. The index of refraction of the first and second cladding layers consisting essentially of Al Ga As Sb can be adjusted to match a variety of types of active cores and to provide a pre-determined divergence.

GaSb-clad mid-infrared semiconductor laser

A video tracking system and a program employing frequency-domain analysis for extracting RHEED intensity oscillation data for film growth on rotating substrates. In initial experiments on GaAs growth, excellent (2%) agreement has been obtained between oscillation frequencies measured for static substrates and substrates with rotation rates as high as 10 rpm. The capability of performing RHEED analysis on rotating substrates could lead to improvements in the quality of complex epitaxial structures and interfaces for which interrupting rotation can have a deleterious effect.

Analysis of Rheed data from rotating substrates

Computerized acquisition and frequency-domain analysis of dynamic reflection high-energy electron diffraction (RHEED) intensity data is obtained during growth by molecular-beam epitaxy (MBE). Rapid, accurate determination of the frequency of RHEED oscillations can be obtained not only when these oscillations are well resolved, but also when the growth conditions yield oscillations that are too poorly resolved to permit frequency analysis by conventional procedures. The method has been used to study transients in the growth of AlGaAs on GaAs substrates and also to investigate the hetero-epitaxial growth of GaAs on Si.

Frequency-domain analysis of RHEED data

Monolithic integration of Si MOSFETs and gallium arsenide MESFETs on a silicon substrate is described herein. Except for contact openings and final metallization, the Si MOSFETs are first fabricated on selected areas of a silicon wafer. CVD or sputtering is employed to cover the wafer with successive layers of SiO.sub.2 and Si.sub.3 N.sub.4 to protect the MOSFET structure during gallium arsenide epitaxy and subsequent MESFET processing. Gallium arsenide layers are then grown by MBE or MOCVD or VPE over the entire wafer. The gallium arsenide grown on the bare silicon is single crystal material while that on the nitride is polycrystalline. The polycrystalline gallium arsenide is etched away and MESFETs are fabricated in the single crystal regions by conventional processes. Next, the contact openings for the Si MOSFETs are etched through the Si.sub.3 N.sub.4 /SiO.sub.2 layers and final metallization is performed to complete the MOSFET fabrication. In an alternative embodiment, Si MOSFETs and aluminum gallium arsenide double heterostructure LEDs are formed in a similar manner.

Monolithic integration of silicon and gallium arsenide devices

A method of compensating grain boundaries or dislocations causing interstices to form particularly in polycrystalline semiconductor materials is disclosed which comprises selectively diffusing opposite impurity-type donor semiconductor material into the interstice to thereby reduce the conductivity of the interstice.

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Chelmsford, MA, United States of America

George W Turner