Engineering topics

Liu, John K.

Publications and source records attributed to Liu, John K..

23 records · Page 2

NASA NTRS1990

MBE growth technology for high quality strained III-V layers

The III-V films are grown on large automatically perfect terraces of III-V substrates which have a different lattice constant, with temperature and Group III and V arrival rates chosen to give a Group III element stable surface. The growth is pulsed to inhibit Group III metal accumulation of low temperature, and to permit the film to relax to equilibrium. The method of the invention: (1) minimizes starting step density on sample surface; (2) deposits InAs and GaAs using an interrupted growth mode (0.25 to 2 monolayers at a time); (3) maintains the instantaneous surface stoichiometry during growth (As-stable for GaAs, In-stable for InAs); and (4) uses time-resolved RHEED to achieve aspects (1) through (3).

Grunthaner, Frank J.↗

NASA NTRS1989

Transient-mode liquid phase epitaxial growth of GaAs on GaAs-coated Si substrates prepared by migration-enhanced molecular beam epitaxy

Planar oxide-maskless growth of GaAs was demonstrated by transient-mode liquid phase epitaxy (TMLPE) on GaAs-coated Si substrates that were prepared by migration-enhanced molecular beam epitaxy (MEMBE). In TMLPE, the cool substrate was brought into contact with hot melts for a short time. A GaAs layer as thick as 30 microns was grown in 10 sec. The etch pits observed in TMLPE-grown layers became longer in one direction and decreased in density with increasing the TMLPE epilayer thickness. The density of etch pits in a 20 micron-thick layer was approximately 5 x 10 the 6th/sq cm. Strong bandgap emission elliptically polarized with a major axis perpendicular to the surface was observed at about 910 nm, while deep-level emission from the TMLPE/MEMBE GaAs interface was detected at 980 nm. The photoluminescence intensity divided by the carrier concentration of the TMLPE-grown layer was about 270 times larger than that of the MEMBE-grown layer used as a substrate.

Nakamura, Shuji↗

NASA NTRS1988

Growth and characterization of GaAs layers on Si substrates by migration-enhanced molecular beam epitaxy

Migration-enhanced molecular beam epitaxial (MEMBE) growth and characterization of the GaAs layer on Si substrates (GaAs/Si) are reported. The MEMBE growth method is described, and material properties are compared with those of normal two-step MBE-grown or in situ annealed layers. Micrographs of cross-section view transmission electron microscopy and scanning surface electron microscopy of MEMBE-grown GaAs/Si showed dislocation densities of 10 to the 7th/sq cm. AlGaAs/GaAs double heterostructures have been successfully grown on MEMBE GaAs/Si by both metalorganic chemical vapor deposition and liquid phase epitaxy.

Kim, Jae-Hoon↗

NASA NTRS1988

High-peak-power low-threshold AlGaAs/GaAs stripe laser diodes on Si substrates grown by migration-enhanced molecular beam epitaxy

A high-peak-power low-threshold AlGaAs/GaAs double-heterostructure stripe laser diode on Si substrats, grown by hybrid migration-enhanced molecular beam epitaxy (MEMBE) and metalorganic chemical vapor deposition (MOCVD) has been demonstrated for the first time. These devices showed the highest peak powers of up to 184 mW per facet reported so far for double-heterostructure stripe laser diodes on Si substrates, room-temperature pulsed threshold currents as low as 150 mA, and differential quantum efficiencies as high as 30 percent without mirror facet coating. An intrinsic threshold current density has been estimated to be about 2 kA/sq cm when taking current spreading and lateral diffusion effects into account. Low dislocation density shows that MEMBE can be a useful method to grow high-quality GaAs and AlGaAs/GaAs layers on Si substrates by combining with MOCVD.

Kim, Jae-Hoon↗

NASA NTRS1988

Al(0.3)Ga(0.7)As / Al(0.05)Ga(0.95)As light-emitting diodes on GaAs-coated Si substrates grown by liquid phase epitaxy

Al(0.3)Ga(0.7)As/Al(0.05)Ga(0.95)As double-heterostructure light-emitting diodes (LEDs) were successfully grown for the first time by liquid phase epitaxy on a GaAs-coated Si substrate that was prepared by a sequential process of migration-enhanced epitaxy and molecular beam epitaxy. The edge-emitting LEDs had diode ideality factors of 1.54 at a forward-biased voltage higher than 0.9 V and external quantum efficiencies of 0.0033 W/A per facet. This efficiency is 50 times higher than the previously reported value, and is on the same order as that of AlGaAs homojunction LEDs fabricated on the GaAs substrates by liquid phase epitaxy.

Sakai, Shiro↗