Inversion-channel Si/SiGe heterojunction field-effect transistor

The p-channel operation of a selfaligned heterojunction field-effect transistor (HFET) based on an Si/Si/sub 0.75/Ge/sub 0.25/ heterostructure is demonstrated. Extrinsic transconductance g/sub m/ greater than 8 mS/mm for a device with 1 mu m gate length was measured at 300 K. The high frequency 3 dB point has been measured to be 1.8 GHz.<>     

Si/SiGe heterojunction bipolar transistor with base doping highly exceeding emitter doping concentration

A Si/Si/sub 0.8/Ge/sub 0.2/ heterojunction bipolar transistor was fabricated having emitter, base and collector contacts at the wafer surface. The base doping concentration amounted to 10/sup 19//cm/sup 3/ which was 20 times the emitter concentration. Due to the pronounced difference in bandgap energy a current gain of 17 was reached.<>     

SiGe drift base bipolar transistor with self-aligned selectiveCVD-tungsten electrodes

A new device and process technology is developed for high-speed SiGe epitaxial base transistors. A 60-nm SiGe epitaxial base and the selectively ion-implanted collector (SIC) structure enhance the cutoff frequency to about 40 GHz. Base resistance is minimized to 165 Ω (emitter area: 0.2×3 μm²), and an f_MAX of 37.1 GHz is achieved by employing 0.2-μm EB lithography for the emitter window, selective CVD tungsten for the base electrode and a self-aligned oxide side wall for the emitter-to-base separation. Circuit simulations predict that this device could reduce the ECL gate delay to below 20 ps     

Quantum study of ultra-thin-base SiGe heterojunction bipolar transistor

A quantum study has been carried out by solving the Schrö;dinger equation for the ultra-thin-base in SiGe heterobipolar transistor. The results are compared with those of the Boltzmann model.     

Reliability of microwave SiGe/Si heterojunction bipolar transistors

The degradation behavior of NPN Si/SiGe/Si heterojunction bipolar transistors, grown by solid-source molecular beam epitaxy (MBE), has been studied by accelerated lifetime testing at different ambient temperatures. The degradations of the dc current gain and the microwave performance of the devices are explained in terms of recombination enhanced impurity diffusion (REID) of boron atoms from the base region and the subsequent formation of parasitic energy barriers at the base-emitter and base-collector junctions     

Low-frequency noise performance of self-aligned InAlAs/InGaAs heterojunction bipolar transistors

The first measurement of low-frequency noise performance for self-aligned InAlAs/InGaAs HBTs is reported. The 1/f noise obtained was around 20 dB lower than that for AlGaAs/GaAs HBTs at a fixed frequency, which is considered to be caused by the low surface recombination velocity of InGaAs.<>     

Low phase noise heterojunction bipolar transistor oscillator

A low phase noise, heterojunction bipolar transistor (HBT) oscillator has been designed and fabricated for operation at X-band. The common emitter oscillator employs a high-Q dielectric resonator as the parallel feedback element between the base and collector terminals. Series capacitive feedback is used in the emitter to enhance the oscillator's negative output impedance. Single-sideband FM noise levels of -76 dBc/Hz and -102 dBc/Hz have been achieved at 1 kHz and 10 kHz frequency offsets, respectively, for an 11.06 GHz carrier frequency. This is one of the lowest phase noise levels ever reported for an X-band solid-state transistor oscillator.<>     

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.     

Self-aligned Ti germanosilicide formation on a polycrystalline Si/SiGe/Si extrinsic base for SiGe heterojunction bipolar transistors

This work reports our investigation of a microstructure of self-aligned Ti germanosilicide made on polycrystalline Si/SiGe/Si multilayers. The existence of the SiGe layer restricted the growth of the Ti germanosilicide layer and produced protrusions penetrating the underlying polycrystalline layer. Each protrusion corresponded to a stacking-faulted single grain of the C49 phase. The microstructure of the thin Ti germanosilicide layer and the deep protrusions caused an increase of the sheet resistance and the contact resistivity of the extrinsic base region. The raised contact resistivity led to a degradation of radio frequency (RF) and noise characteristics of the SiGe heterojunction bipolar transistor (HBT).     

Novel process for emitter-base-collector self-aligned heterojunction bipolar transistor using a pattern-inversion method

A process for base-emitter-collector self-aligned HBTs using a pattern-inversion method is presented. A fabricated HBT has an emitter with a size of 1.5 × 10?m2 realised by employing a dry-etching method. Typical current gain for the fabricated HBT is 26.     

AlGaN/GaN heterojunction bipolar transistor

We demonstrate the first GaN bipolar transistor. An AlGaN/GaN HBT structure was grown by MOCVD on c-plane sapphire substrate. The emitter was grown with an Al_0.1Ga_0.9N barrier to increase the emitter injection efficiency. Cl₂ RIE was used to pattern the emitter mesa, and selectively regrown base contact pads were implemented to reduce a contact barrier associated with RIE etch damage to the base surface. The current gain of the devices was measured to be as high as three with a base width of 200 nm. DC transistor characteristics were measured to 30 V V_CE in the common emitter configuration, with an offset voltage of 5 V. A gummel plot and base contact characteristics are also presented     

Waveguided electro-optical intensity modulation in a Si/Ge/sub x/Si/sub 1-x//Si heterojunction bipolar transistor

Optical phase-and-amplitude modulation at 1.55 mu m in an electro-optic guided-wave Si/Ge/sub 0.2/Si/sub 0.8//Si HBT is investigated using computer-aided modelling and simulation. At an injection of 10/sup 19/ electrons per cm/sup 3/, an intensity modulation of 10 dB is predicted for an active length of 390 mu m.<>     

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.     

Properties of a poly-Si/GaAs layered structure on Si for Si heterojunction bipolar transistor

The properties of poly-Si/GaAs layered films on Si for use in wide bandgap emitters for Si heterojunction bipolar transistors (Si-HBTs), were studied. A smooth GaAs film surface grown on Si was obtained at low temperature (200° C) from the initial stage of growth. The x-ray diffraction (XRD) results indicated that strong GaAs orientation (111) was obtained for the poly-Si/GaAs/Si-substrate layered structure after annealing at 800° C for 20 sec. Secondary ion mass spectroscopy (SIMS) profiles indicated that impurity diffusion from the GaAs layer into the p-type Si substrate was negligible at 800° C. The electrical characteristics forn-poly-Si/n-GaAs/p-Si-substrate heterojunction diodes were also investigated.     

GaAlAs/GaAs heterojunction microwave bipolar transistor

A GaAlAs/GaAs heterojunction bipolar transistor has been developed and tested. A double base structure was adopted to facilitate critical selective etching problems. An emitter-collector breakdown voltage VCEO as high as 80 V was achieved. Maximum frequency of oscillationfmax of 850 MHz and a cutoff frequency fT of 1.6 GHz were realised. The current-gain/temperature curve shows that the transistor can be operated at temperatures up to 350°C.     

Submicrometer fully self-aligned AlGaAs/GaAs Heterojunction bipolar transistor

A novel submicrometer fully self-aligned AlGaAs/GaAs heterojunction bipolar transistor (HBT) for reducing parasitic capacitances and resistances is proposed. The fabrication process utilizes SiO2sidewalls for defining base electrode width and separating this electrode from both emitter and collector electrodes. Measured common-emitter current gain β for a fabricated HBT with 0.6 × 10-µm²emitter dimension and 0.7 × 10-µm²× 2 base dimension is 26 at 9 × 10⁴-A/cm²collector current density.     

Measurement and comparison of 1/f noise and g-r noise in siliconhomojunction and III-V heterojunction bipolar transistors

This paper experimentally determines and compares the 1/f noise and the g-r noise, as components of the base noise current spectral density, in Si homojunction and III-V heterojunction bipolar transistors (HBTs) in common-emitter configuration. The noise spectra for each of these devices are obtained as functions of the base bias current (I_B), and the 1/f noise has been found to depend on I_B as I_B^γ, where γ~1.8 for the silicon BJT's and InP/InGaAs HBT's with high current gains (β~50), and γ~1.1 for the AlGaAs/GaAs HBTs with low current gains (4<β<12). The nearly constant current gain and the near square-law and inverse-square emitter area dependence of 1/f noise in silicon devices are indicative of the dominant base bulk recombination nature of this noise. The 1/f noise in the InP based HBTs has been found to be lowest among all the devices we have tested, and its origin is suggested to be the base bulk recombination as in the Si devices. For the AlGaAs/GaAs HBTs, the low current gain and the near unity value of γ, arise most likely due to the combined effects of surface, bulk, and depletion region recombinations and the base-to-emitter injection. The dependence of the 1/f noise on the base current density in the devices tested in this work, and those tested by others are compared to find out which HBT's have achieved the lowest level of 1/f noise     

16 Gbit/s multiplexer IC using double mesa Si/SiGe heterojunction bipolar transistors

A double mesa Si/SiGe heterojunction bipolar transistor (HBT) was developed for application in integrated circuits. The HBT is characterised by an emitter base heterojunction and consequently by a high base doping concentration. By using these transistors an integrated digital circuit, a multiplexer, was implemented. The measured bit rate of this first Si/SiGe HBT circuit was 16 Gbit/s.<>     

Avalanche-induced 1/f noise in bipolar transistors

It has been proposed that degradation of low current hFE, as a result of avalanching the emitter-base junction of a bipolar transistor, can be attributed to an increase in surface recombination velocity within the emitter-base space-charge region. This work shows that 1/fnoise is also increased during avalanche and that this increase is consistent with a previously reported correlation between surface recombination velocity and 1/fnoise.