77K下电流增益为2.6万的SiGe/Si HBT

通过优化设计SiGe/SiHBT的纵向参数,找到一种低温工艺方法,研制出了在液氮温度下电流增益达到26000的高增益异质结晶体管。     

Influence of the oxygen content in SiGe on the parameters of Si/SiGe heterojunction bipolar transistors

We demonstrate peak f_T and f_max of 50 GHz for heterojunction bipolar transistors (HBTs) with an oxygen concentration in the epitaxial SiGe base layer of about 10²⁰ cm⁻³. These f_T/f_max values are over 10 GHz higher than for identically processed HBTs with an O content of only 10¹⁸ cm⁻³. This is due to reduced transient enhanced diffusion of boron in the O-rich layers. However, the base carrier lifetimes are reduced by the high oxygen content. We show that ideal base current characteristics and a low 1/fnoise level can be obtained despite this effect by localizing the emitter-base space-charge region outside the O-rich layer.     

Simulation analysis of the DC current gain in an n-p-n a-Si:H/SiGe/Si heterojunction bipolar transistor

This paper presents the results of a simulation study focused on the evaluation of the DC characteristics of an n-p-n SiGe-based heterojunction bipolar transistor (HBT) performing an extremely thin n⁺ hydrogenated amorphous silicon (a-Si:H) emitter. The a-Si:H(n)/SiGe(p) structure exhibits an energy gap difference of approximately 0.8 eV mostly located at the valence band side and this results in an optimal configuration for the emitter/base junction to improve the emitter injection efficiency and thus the device performance.Considering a 20% Ge uniform concentration profile in the base region, simulations indicate that the DC characteristics of an a-Si:H/SiGe HBT are strictly dependent on two essential geometrical parameters, namely the emitter width and the base width. In particular, the emitter thickness degrades device characteristics in terms of current handling capabilities whereas higher current gains are obtained for progressively thinner base regions. A DC current gain exceeding 9000 can be predicted for an optimized device with a thin emitter and a 10 nm-thick, doped base.     

Two-dimensional simulations of amplification of space charge waves in a strained Si/SiGe heterostructure at 77 K

We theoretically investigated the propagation and amplification of space charge waves on the surface of a strained Si/SiGe heterostructure at 77 K, using the negative differential conductance phenomenon. In this work, we also have done a comparison between the n-GaAs thin film and strained Si/SiGe heterostructure with respect to the propagation of space charge waves. We have obtained results in 2D of propagation and amplification of space charge waves in a strained Si/SiGe heterostructure until for frequencies f<40 GHz.     

Control of implant-damage-enhanced boron diffusion in epitaxially grown n-Si/p-Si1-xGex/n-Si heterojunction bipolar transistors

Boron out-diffusion in epitaxially grown n-Si/p⁺-Si_1-xGe_x/n-Si heterojunction bipolar transistors is significantly enhanced during 850°C, 10 s rapid thermal annealing following arsenic emitter contact implantation. In this paper, we introduce three techniques which dramatically reduce boron out-diffusion during implant activation. Limiting the post-implant processing to 600°C for 2 min results in minimal diffusion giving acceptable device performance. A second technique involves pulsed laser annealing of the As implant, which removes residual defects and eliminates enhanced diffusion during subsequent thermal processing. Finally, we show that high bulk concentrations of oxygen in the Si_1-xGe_x (∼10²⁰ cm^-3) dramatically reduce the implant-damage-enhanced boron diffusion. In addition to the depth profiles, electrical measurements performed on heterojunction bipolar transistors, incorporating these fabrication techniques, show ideal collector current characteristics and confirm the absence of deleterious boron out-diffusion effects.     

Effects of high temperature annealing on the device characteristics of Ga0.52In0.48P/GaAs and Al0.52In0.48P/GaAs heterojunction bipolar transistors

GaInP/GaAs and AlInP/GaAs heterojunction bipolar transistor (HBT) structures were grown by low pressure metalorganic vapor phase epitaxy and annealed at various temperatures up to 675°C for 15 min. Subsequent comparisons with HBTs fabricated on both annealed and unannealed control samples showed no effects for annealing up to and including 575°C, but significant changes in the electrical characteristics were observed at an annealing temperature of 675°C. For the GaInP/GaAs devices, the base current increased by a significant amount, reducing the gain and increasing the base current ideality factor from 1.07 to 1.9. Photoluminescence and electrical measurements on the structures indicated that both the emitter and base were affected by an increase in the recombination times in those regions. These effects were attributed to an out-diffusion of hydrogen from the base during annealing. The emitter of the AlInP/GaAs HBT was affected less by the hydrogen diffusion because of the larger bandgap. These observations have important implications for device performance dependence on the details of the temperature/time profile subsequent to the base growth.     

Thermal characteristics of InP, InAlAs, and AlGaAsSb metamorphic buffer layers used in In0.52Al0.48As/In0.53Ga0.47As heterojunction bipolar transistors grown on GaAs substrates

In_0.52Al_0.48As/In_0.53Ga_0.47As heterojunction bipolar transistors (HBTs) were grown metamorphically on GaAs substrates by molecular beam epitaxy. In these growths, InAlAs, AlGaAsSb, and InP metamorphic buffer layers were investigated. The InAlAs and AlGaAsSb buffer layers had linear compositional grading while the InP buffer layer used direct binary deposition. The transistors grown on these three layers showed similar characteristics. Bulk thermal conductivities of 10.5, 8.4, and 16.1 W/m K were measured for the InAlAs, AlGaAsSb, and InP buffer layers, as compared to the 69 W/m K bulk thermal conductivity of bulk InP. Calculations of the resulting HBT junction temperature strongly suggest that InP metamorphic buffer layers should be employed for metamorphic HBTs operating at high power densities.