摘要:

Reactive ion etching (RIE) of epitaxial, strained Si1−xGexalloys,x≤0.20, in fluorine‐, chlorine‐, and bromine‐based low‐pressure plasmas has been investigated. The SiGe etch rates increase for each etchant with Ge concentration, e.g., for fluorine‐based RIE (CF4and SF6) the etch rate of a Si80Ge20alloy is &bartil;2xthat of elemental Si. Analysis shows that the etch rate increase is not accounted for by the greater rate of gasification of Ge atoms alone but that the presence of Ge atoms in the SiGe alloy increases the rate of Si etch product formation.

ISSN:0003-6951    

DOI:10.1063/1.104942

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Highly strained In0.33Ga0.67As/AlAs‐based resonant tunneling diodes have been fabricated on GaAs(100) substrates without the use of thick strain relieving buffer layers. These structures exhibit a simultaneously high peak current density (Jp) of 125 kA/cm2and a peak to valley ratio (PVR) of 4.7. A PVR of 5.9 withJp=73 kA/cm2is observed on some devices, the highest PVR seen for such devices. The excellent resonant tunneling characteristics of these devices are attributed to accurate device design using a &Ggr;‐X‐&Ggr;‐X‐&Ggr; resonant tunneling path and to high quality interfaces obtained through the use of optimized growth conditions.

ISSN:0003-6951    

DOI:10.1063/1.104943

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Electron transport in quantum well modulation &dgr; doped on either the normal or the inverted side has revealed the major cause of the long‐puzzling inferior transport characteristics of the inverted interface. For growth conditions optimized for best transport with normal‐side doping, we find migration of the Si dopant toward the inverted interface during growth to be the primary reason for the reduced inverted well mobility. This new understanding has allowed us to grow modulation‐doped inverted quantum wells of unprecedented quality having electron mobilities as high as 2.4×106cm2/V s at 4.2 K and 3.0×106cm2/V s at 1.0 K.

ISSN:0003-6951    

DOI:10.1063/1.104915

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A real‐time reflectance‐difference spectroscopy (RDS) study of surface reactions of trimethylgallium (TMGa) and tertiarybutylarsine (TBAs) with (001)GaAs surfaces in an ultrahigh vacuum environment is reported. These studies reveal several phases of atomic layer epitaxy of GaAs using TMGa. A model consistent with various kinetics studies is established to explain the distinct behavior observed in RDS during TMGa exposures. It is shown that optimal growth conditions can be achieved through RDS monitoring. The self‐limiting mechanism which occurs in TMGa exposure cycle is believed to result from both selective adsorption and reaction of TMGa at As atoms and Ga vacancy induced Ga‐rich surface reconstruction. It is also shown that TBAs is a promising arsenic source for atomic layer epitaxy.

ISSN:0003-6951    

DOI:10.1063/1.104916

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Long wavelength quantum well detectors with very high quantum efficiency, based on the coupling of radiation into an optical resonant cavity or waveguide defined by a reflection grating coupler on one side of the infrared absorbing multiquantum well stack, and an aluminum arsenide cladding layer on the other, have been fabricated and the results compared with theory. Theory shows that quantum efficiencies up to 90% may be obtained (for polarized radiation). However, experimental results indicate that the response peak becomes broadened due to spread in the grating period and therefore the maximum quantum efficiency is in practice limited to 60%, corresponding to a current responsivity of 2.1 A/W. This is 2.7 times larger than for a 45° polished edge detector with the same quantum well characteristics.

ISSN:0003-6951    

DOI:10.1063/1.104917

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report a rapid thermal annealing (RTA) enhancement of the structural coherence of Si‐implanted InxAl1−xAs (x≊0.54) layers on (100)InP. Under these annealing conditions (750 °C for 30 s), the enhancement occurs only in implanted samples and is characterized by the appearance of pendello¨sung fringes in double‐crystal x‐ray diffraction. Measurements of the parallel (&egr;∥) and perpendicular (&egr;⊥) lattice mismatch show a slight relaxation in &egr;⊥during RTA without significant generation of dislocations (&egr;∥=0). The results suggest an electronic mechanism for the increased efficiency of RTA in implanted samples.

ISSN:0003-6951    

DOI:10.1063/1.104895

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Optical transmission spectra of CuCl microcrystals embedded in NaCl crystals were studied around theZ3exciton resonance by varying the annealing time. With the increase in the annealing time, extinction spectra of theZ3exciton change anomalously from the absorption‐type spectrum to the emission‐type spectrum via the dispersion‐type spectrum. The Mie theory [Ann. Phys.25, 377 (1908)] successfully explains the spectral change due to the growth of microcrystals. We report here for the first time an anomalous change of the exciton spectra due to the growth of semiconductor microcrystals.

ISSN:0003-6951    

DOI:10.1063/1.104896

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have investigated the effects of rapid thermal annealing on the electrical and optical properties of planar‐doped AlGaAs/InGaAs/GaAs high electron mobility transistor structures grown by molecular beam epitaxy. Hall effect and photoluminescence measurements on samples with In0.22Ga0.78As and In0.28Ga0.72As channels reveal a temperature‐dependent degradation in sheet charge density, Hall mobility, and photoluminescence response. The structures were essentially stable through the temperature range used in normal device processing. However, annealing temperatures greater than 700 °C resulted in strain relaxation and layer intermixing, especially for the In0.28Ga0.72As sample.

ISSN:0003-6951    

DOI:10.1063/1.104897

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Heteroepitaxial MBE growth of Ge on Si(100) is studied at temperatures down to room temperature. We show that, as for Si and GaAs homoepitaxy, the low‐temperature limit to growth is an epitaxial thickness,hepi, before the amorphous phase is nucleated.hepiincreases with increasing temperature with an apparent activation energy of 0.5±0.1 eV at 0.2 A˚/s. Above 170 °Chepiincreases discontinuously and becomes effectively infinite, possibly as solid phase begins to occur. We show that growth is planar for all temperatures below 300 °C, so that low‐temperature growth can be used near 200 °C to suppress island formation without encountering the limited thickness effect. In contrast with planar growth at high temperatures with an As ‘‘surfactant’’, strain relaxation of these planar epilayers occurs by normal dislocation introduction to give an array of predominantly edge misfit dislocations.

ISSN:0003-6951    

DOI:10.1063/1.104898

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A theoretical study of hole wave packets in a GaAs, Al0.3Ga0.7As superlattice is presented. Formation of the wave packet by short laser pulse excitation and the time‐dependent nature of the wave packet are discussed, with particular attention given to the quasi‐periodic nature of the time dependence. Phenomena analogous to those displayed in atomic and molecular wave packet systems are predicted. The wave packet formalism provides a powerful tool for studying coherent hole dynamics, including quantum beat phenomena, and could be useful in determining heavy and light hole relaxation rates.

ISSN:0003-6951    

DOI:10.1063/1.105234

出版商:AIP    

年代:1991

数据来源: AIP