H. P. Meier

Nanometer resolution in luminescence microscopy of III‐V heterostructures

In a scanning tunneling microscope experiment, the luminescence induced by the recombination of holes with electrons tunneling into cleaved (110) GaAs/AlGaAs heterostructures is used to image the interface region with nanometer resolution.

Tunneling microscopy and spectroscopy of molecular beam epitaxy grown GaAs-AlGaAs interfaces

We report the first observation of GaAs/AlGaAs compound multilayers and interfaces at atomic scale resolution. Using a scanning tunneling microscope, the atomic registry in the epitaxial layers and their interfaces was observed. The semiconductor band gaps and valence‐band offsets relative to the Fermi level are obtained via local spectroscopy in the GaAs and AlGaAs multilayers.

5.2-GHz bandwidth monolithic GaAs optoelectronic receiver

A high-speed monolithic optoelectronic receiver consisting of a photodetector, a transimpedance amplifier and a 50- Omega output buffer stage has been fabricated using an enhancement/depletion 0.35- mu m recessed-gate GaAs MESFET process. The interdigitated metal-semiconductor-metal photodetector has a dark current of 0.8 nA, a responsivity of 0.2 A/W, and a capacitance of 12 fF. The bandwidth of the receiver is 5.2 GHz with an effective transimpedance of 300 Omega into a 50- Omega load, which corresponds to a transimpedance bandwidth product of 1.5 THz- Omega .<<ETX>>

Indium adatom migration during molecular beam epitaxial growth of strained InGaAs/GaAs single quantum wells

Indium composition variations in strained InGaAs/GaAs quantum wells grown on nonplanar substrates by molecular beam epitaxy have been analyzed by spatially and spectrally resolved low‐temperature cathodoluminescence. For our growth conditions, the In adatom migration length on (100) facets has been determined to be ∼25 μm. A maximum relative increase of In incorporation of ≂6% on (100) ridges is observed and is found to be strain independent (In composition) for quantum wells nominally 35 and 70 A thick with In composition of 0.10–0.22. Significantly asymmetric indium adatom migration is observed between adjacent (100) facets for ridges and grooves formed with (111)A and (311)A multifaceted sidewalls, indicating that multifaceting kinetically inhibits adatom migration. For structures designed for one‐step growth of index‐guided injection lasers with built‐in nonabsorbing waveguides, we show that differences greater than 80 meV in the effective band gap of a 70 A quantum well can be achieved between the ga...

Scanning tunneling microscopy and potentiometry on a semiconductor heterojunction

The potential distribution across the cleaved end face of a forward‐biased GaAs double heterojunction laser diode was mapped using scanning tunneling potentiometry. Space‐charge regions next to the heterojunction interface as well as the electron‐hole recombination region within the active layer are outlined with nanometer resolution. The carrier injection zone in the active layer is observed as a function of junction voltage.

Ga adatom migration over a nonplanar substrate during molecular beam epitaxial growth of GaAs/AlGaAs heterostructures

Thickness variations in GaAs/AlGaAs quantum wells grown on patterned substrates by molecular beam epitaxy have been analyzed by spatially and spectrally resolved low‐temperature cathodoluminescence. For the lower and upper (100) facets joined by an angled (311)A facet, relative increases in quantum well thicknesses up to ≂6% and 20% are observed, respectively, in the vicinity of the intersection of the facets. Following an exponential behavior, the Ga adatom migration length is found to be in the range of 1–2 μm on both the lower and upper (100) facets and is independent of quantum well thickness. This migration length is orders of magnitude greater than previously reported for Ga adatoms during molecular beam epitaxy growth.

Very high-power (425 mW) AlGaAs SQW-GRINSCH ridge laser with frequency-doubled output (41 mW at 428 nm)

A very high-power AlGaAs single-quantum-well graded-index separate confinement heterostructure (GRINSCH) ridge laser operating in a diffraction-limited fundamental transverse mode up to 360 mW at a wavelength of 856 nm is presented. The maximum power output of the laser reached 425 mW, limited by thermal saturation of the device and not by catastrophic optical mirror damage. These lasers exhibit very high power levels and show excellent reliability at high output power levels. The extremely high, continuous-wave (CW) fundamental mode power combined with very low-intensity and optical phase distortion as well as low astigmatism render this ridge waveguide laser suitable for optical storage systems, printers, and direct frequency doubling. These devices have been successfully used for direct-frequency doubling of their output in a resonant KNbO/sub 3/ cavity yielding 41 mW of blue radiation at 428 nm. >

Energy dependence and depth distribution of dry etching‐induced damage in III/V semiconductor heterostructures

We have investigated the depth distribution, energy dependence, and the effect of the angle of incidence of ion beam etching (IBE) induced damage. Our technique is based on the partial etching of the upper GaAlAs barrier of a GaAs single quantum well (SQW) layer. The optical emission of the SQW at low temperatures is used as a local probe for the created damage. The dependence of the quantum efficiency on the etch depth can be described by a Gaussian depth distribution with a typical decay length of 5.6 nm and a non‐Gaussian long range tail. Our measurements show a strong dependence of the dry etch damage on the angle of incidence of the ion beam and on the sample orientation.

Problems related to the formation of lateral p–n junctions on channeled substrate (100) GaAs for lasers

We shall describe the main steps required for molecular‐beam epitaxial (MBE) growth on structured GaAs substrates for lasers, in particular, a reproducible etching process develolped for GaAs which yields well‐defined and controllable tilt angles. The main parameters determining morphology and doping behavior on a facet are tilt angle Θ, substrate temperature, and the V:III ratio. The limiting values of these three parameters for obtaining good quality n‐ and p‐type films, using Si as a dopant, will be determined. We conclude that a (311A) facet is best suited to obtain plane selective doping without generating a detrimental (111A) plane. As a result of this study, lateral p–n junctions with light emission will be demonstrated showing promise for new device structures such as lasers.

Investigations on resonant tunneling in III‐V heterostructures

We present data obtained on a set of symmetric GaAs/AlGaAs double‐barrier quantum‐well structures in which the thickness of the AlGaAs barriers has been systematically varied from 31 to 7.5 nm. Low‐temperature I(V ) characteristics, temperature dependencies, and magnetotunneling have been investigated. Our data suggest a dominance of sequential tunneling processes in the range investigated and point to interface roughness in the well as the possible cause for the large valley currents. Our best devices exhibit a current peak‐to‐valley ratio of about 20.