The properties of a highly selective chemical etchant composed of hydrofluoric acid, hydrogen peroxide, and acetic acid (HF:H202:CH3COOH) is investigated in etching SiGe/Si heterostructures. This solution has been found to etch Si~_= Ge~ much faster than Si over the entire range of Ge contents. The etch rate dependences are presented as functions of solution composition, Ge content, dopant type, diluent type, temperature, and stirring. Both n-type and p-type Si~ =Ge= layers with Ge contents of 0 -< x -< 0.60 and 0 ~ x <-1.00, respectively, are investigated. It is found that the n-type samples etch at a faster rate than p-type for all Ge contents examined. When CH3COOH is used as the diluent instead of H20 a significant enhancement in the etch rate results for all concentrations of Ge studied. Also, the amount of H202 in the presence of CH3COOH has a significant effect on the magnitude of the etch rate as well as its behavior over time.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 169.230.243.252 Downloaded on 2014-11-26 to IP
Ge0.5Si0.5 strained-layer pin photodiodes, in which multiple strained layers serve as the absorption region, have been fabricated. These devices exhibit an optical response at wavelengths beyond 1.3 μm at normal incidence. The measured external quantum efficiencies at an applied bias of 4 V are 17% at 0.85 μm and 1% at 1.3 μm, respectively. Excellent electrical characteristics evidenced by the avalanche breakdown at 20 V have also been demonstrated.
In this paper, we review recent progress in SiGe MOS technology. Progress in high mobility p-channel and n-channel devices will be presented as well as some of the materials and processing issues related to the fabrication of these heterostructures. In addition, we will present an outlook on the integration of these devices to complimentary MOS (CMOS) based on Si on Insulator technology (SOl). New directions of novel devices utilizing selective epitaxial growth and the integration of Si/Ge superlattices for enhanced performance in field effect transistors are described. Finally, we will examine some of the materials challenges of integrating SiGe technologies with current CMOS production processes.
A 48 m cutoff wavelength (c) Si far-infrared ͑FIR͒ detector is demonstrated. Internal photoemission over a Si interfacial work-function of a homojunction consisting of molecular beam epitaxy grown multilayers (p ϩ emitter layers and intrinsic layers͒ is employed. The detector shows high responsivity over a wide wavelength range with a peak responsivity of 12.3Ϯ0.1 A/W at 27.5 m and detectivity D* of 6.6ϫ10 10 cmͱHz/W. The c and bias dependent quantum efficiency agree well with theory. Based on the experimental results and the model, Si FIR detectors ͑40-200 m͒ with high performance and tailorable c s can be realized using higher emitter layer doping concentrations.
We report on the growth and characterization of high-quality strain-relaxed SiGe alloys on a compliant silicon–on–insulator (SOI) substrate. The annealing temperature required for strain transfer has been reduced through boron implantation to the buried oxide, leading to a high quality SiGe alloy free from dislocations as evident from the near-band gap photoluminescence. Nearly complete strain relaxation (∼95%) for SiGe alloy of a thickness beyond the conventional critical thickness has been obtained.
The variation of barrier height with the band gap in the metal/heterojunction systems is related to how the Fermi level position varies with respect to band edges. If the Fermi level is pinned by the interface states its movement will also correspond to the movement of the neutrality level at the interface. Metal/Si1−xGex/Si heterostructures (0⩽x⩽0.24) for both n- and p-type substrates were studied to understand the relation between Schottky barrier, Fermi level movement, and the band gap variations. It was shown that a correlation exists between Schottky barrier height variation and band-offset values ΔEc and ΔEv. For n-type substrate, measured barrier height differences are almost the same as the band offsets in the conduction band ΔEc. For p-type substrates they were found to be slightly smaller than ΔEv. This shows that Fermi level position relative to the conduction band edge does not change with band gap variation.
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