Chin-An Chang

Optical absorption of In1−xGaxAsGaSb1−yAsy superlattices☆

Abstract The formation of subbands in In 1−x Ga x AsGaSb 1−y As y superlattices has resulted in entirely different absorption characteristics from those of the host semiconductors. The measured absorption edges agree with the calculated energy gaps of the superlattices of various configurations, establishing that the conduction bandedge of InAs lies approximately 0.15eV below the valence bandedge of GaSb.

Two-dimensional electronic structure in InAs-GaSb superlattices☆☆☆

Abstract We have achieved by molecular-beam-epitaxy the new type of superlattice of InAs and GaSb whose energy gaps do not overlap. The observed Shubnikov-de Haas oscillations manifest the two-dimensional electronic subband structure, corroborating theoretical calculations. The deduced electron mass is enhanced primarily as a result of the strong nonparabolicity in the conduction-band of InAs.

Ion backscattering and channeling study of InAs‐GaSb superlattices

We show that the Rutherford backscattering yield from [100] InAs‐GaSb superlattices has a marked oscillatory structure indicative of the superlattice periodicity. Channeling measurements reveal higher dechanneling along 〈110〉 than along [100] directions, and this can be interpreted as an evidence for relaxation effects along the [100] growth direction at each InAs‐GaSb interface. We attribute this to the fact that, although there is a good lattice match between InAs and GaSb, the interfaces consist of either Ga–As or In–Sb bonds, which differ by 7% in binding distance from InAs‐GaSb.

MAGNETIC AND MAGNETO-OPTIC PROPERTIES OF THICK FACE-CENTERED-CUBIC CO SINGLE-CRYSTAL FILMS

The present letter describes for the first time the magnetic and magneto‐optical properties of thick fcc cobalt single‐crystal films (≂1000‐A thickness). The magneto‐crystalline anisotropy constants K1 and K2 are about −7.2×10 erg/cc and 2×10 erg/cc at 77 K, respectively. Both decrease in magnitude with increasing temperature in a range from 77 K to about 450 K. The easy axis is found to be 〈111〉. The polar Kerr angle for the fcc phase is much larger than that of the hcp phase by 0.1°–0.2° in a photon energy range from about 1 to 5 eV.

Quantized Hall Effect in Single Quantum Wells of InAs

Abstract We report magnetotransport measurements, down to 0.55 K and up to 28 T, on GaSb-InAs-GaSb heterostructures. At moderate and high fields, the magnetoresistance vanishes and the Hall resistance shows plateaus at values of h ie 2 when i ( i = 1, 2, 3, …) magnetic levels are fully occupied. In addition, in high mobility samples, new features appear, the most prominent being a plateau at i = 5 2 . The characteristics of these features are different from those observed in GaAs-GaAlAs at fractional occupation numbers, suggesting that they are likely related to the presence of holes in this system.

Semimetallic InAs-GaSb Superlattices to the Heterojunction Limit,

Superlattices of InAs‐GaSb have been investigated with layer thicknesses ranging from the onset of the semiconductor‐semimetal transition (<100 A) to the heterojunction limit (≳1000 A). Pronounced Shubnikov–de Haas osicillations have been observed throughout the entire semimetallic regime which are shown to be associated with the ground‐electron sub‐bands, yielding energies of the Fermi level in agreement with those calculated from electron transfers.

Magnetic field‐induced semimetal‐to‐semiconductor transition in InAs‐GaSb superlattices

With the application of a magnetic field, we have observed a semimetal‐to‐semiconductor transition in InAs‐GaSb superlattices with closely overlapped subbands of electrons and holes. The transition is manifested in a sharp increase in the magnetoresistance in the quantum limit, where the ground Landau levels associated with the subbands are crossed at the Fermi level, resulting in carrier depletion.

Quantum wells of InAs between AlSb

Quantum wells consisting of a single InAs layer confined between two AlSb layers were made. and they exhibited characteristic two-dimensional electron behavior from magneto-transport measurements. Unexpectedly, the electrons appeared to be predominantly extrinsic in nature. unlike the situation in the InAs-GaSb system.

Resonant Raman Scattering in GaSb-AlSb Superlattices

The electronic properties of GaSb-AlSb superlattices (SL) have been recently analyzed by different experimental techniques showing unambiguously the formation of electronic subbands at the Γ-point 1-2. To our knowledge, the only reported information 1 on the band structure away from the Brillouin zone center is supplied by electroreflectance measurements. They show some features probably related to E1 and E1+Δ1 transitions at the bulk materials. In this communication we analyze the electronic structure of GaSb-AlSb SL associated with the E1 transition of GaSb by resonant Raman scattering. The studied samples are a GaSb single crystal and two SL grown on (001)GaSb substrates. The first SL (labeled as 26-20) has 65 periods each one containing 26 layers of GaSb and 20 of AlSb. The second SL (labeled as 52-20) has 45 periods each one with 52 layers of GaSb and 20 of AlSb. In all cases, Raman spectra are taken in back-scattering configuration on the (001) epitaxial surfaces at temperatures ranging from to 300°K. A Rhodamine (110 or 6G) dye laser pumped by an Argon laser is used. All the spectra are referred to the CaF2 standard. Since we are interested in the electronic structure associated with the L point of GaSb, we analyze the peak of the Raman spectrum coming from the L0 phonon of GaSb which is mostly confined in the layers of this semiconductor.