Zhenqiang Ma

A high-power and high-gain X-band Si/SiGe/Si heterojunction bipolar transistor

A double mesa-type Si/SiGe/Si (n-p-n) heterojunction bipolar transistor (HBT) with record output power and power gain at X-band (8.4 GHz) is demonstrated. The device exhibits collector breakdown voltage BV/sub CBO/ of more than 24 V and a maximum oscillation frequency f/sub max/ of 37 GHz. Under continuous-wave operation and class-AB biasing conditions, 24.2-dBm (263-mW) RF output power with concurrent gain of 6.9 dB is measured at the peak power-added efficiency (28.1%) from a single ten-emitter fingers (780-/spl mu/m/sup 2/ emitter area) common-base HBT. The maximum RF output power achieved is as high as 26.3 dBm (430 mW in saturation) and the maximum collector efficiency is 36.9%. The low collector doping concentration together with the device layout result in negligible thermal effects across the transistor and greatly simplifies the large-signal modeling. The conventional Gummel-Poon model yields good agreement between the modeled and the measured de characteristics and small-signal S-parameters. The accuracy of the model is further validated with the measured power performance of the SiGe power HBT at X-band. These results set a benchmark for power performance for SiGe-based HBTs and indicate promise for their implementation in efficient X-band power-amplifier circuits.

An X-band high-power amplifier using SiGe/Si HBT and lumped passive components

We report the design and fabrication of a compact microwave monolithic integrated circuit (MMIC) amplifier, which demonstrates high output power at X-Band. A single-stage power amplifier is demonstrated, with a double-mesa type SiGe/Si HBT as the active device and spiral inductors and MIM capacitors as lumped passive components. At 8.4 GHz, a linear gain of 8.7 dB, an output power at peak efficiency of 23 dBm, and a saturated output power P/sub sat/ of 25 dBm, are measured. To our knowledge, this is the first MMIC X-Band power amplifier using SiGe/Si HBTs.

SiGe/Si power HBTs for X- to K-band applications

High performance power SiGe/Si HBTs at X-band (8.4 GHz), Ku-band (12.6 GHz) and K-band (18 GHz) have been demonstrated. Under continuous wave operation, a single 20-finger Si/Si/sub 0.75/Ge/sub 0.25//Si (emitter area of 1200 /spl mu/m/sup 2/) HBT, biased in class AB, delivers 28.5 dBm (700 mW) of RF output power at X-band, 25.5 dBm (350 mW) at Ku-band and 22.5 dBm (180 mW) at K-band. These represent the state-of-the-art power performance of SiGe-based HBTs at frequencies above X-band. An in-depth analysis of the power performance of HBTs with different geometry and configuration is also presented, which will eventually serve as a design guide for SiGe/Si power HBTs at different operating frequencies.

An 8.4 GHz SiGe/Si HBT-based MMIC power amplifier

A single-stage X-band MMIC power amplifier incorporating a SiGe/Si power HBT and lumped passive components is reported. The power HBT is characterized by an f/sub max/ of 67 GHz and a BV/sub CBO/ of more than 24 V. The matching circuits were designed for maximum output power using on-chip spiral inductors and SiO MIM capacitors. Continuous wave measurements were made at 8.4 GHz, under class A operation. The power amplifier demonstrated a linear gain of 8.6 dB, output power at peak efficiency of 22.9 dBm and a saturated output power of 24.8 dBm.

SiGe power heterojunction bipolar transistors (HBTs) fabricated by fully self-aligned double mesa technology

Multi-finger SiGe HBTs have been fabricated using a novel fully self-aligned double-mesa technology. With the advanced process technology, a maximum oscillating frequency (f/sub max/) of 78 GHz and a cut-off frequency (f/sub T/) of 37 GHz were demonstrated for a common-emitter device with emitter area of 2/spl times/2/spl times/30 /spl mu/m/sup 2/. For class-A operations, 10-finger devices (A/sub E/=2/spl times/2/spl times/30 /spl mu/m/sup 2/) exhibit an output power of 24.13 dBm with a maximum power added efficiency (PAE) of 26.9% at 8.5 GHz.

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.

Small- and large-signal operation of X-band CE and CB SiGe/Si power HBT's

Common-emitter (CE) and common-base (CB) multifinger SiGe/Si power heterojunction bipolar transistors (HBTs) for X-band operation are reported for the first time. 10-finger CB and CE devices show f/sub max/ of 28 GHz and 20 GHz, maximum PAE of 34.9% and 17.5%, and P/sub out/ at 1 dB gain compression point of 15.6 dBm and 17.5 dBm, respectively, in class A operation at 8 GHz for CW mode.

Power performance of X-band Si-Si/sub 0.75/Ge/sub 0.25/-Si HBTs

High performance power SiGe-Si HBTs at X-band (8.4 GHz) frequency have been demonstrated. Under continuous wave operation, a single 10-finger Si-Si/sub 0.75/Ge/sub 0.25/-Si (emitter area of 780 /spl mu/m/sup 2/) HBT, biased at class AB, exhibits 29% peak PAE operating in common-emitter (C-E) mode and 42.1% peak PAE in common-base (C-B) mode with 25.7 dBm and 25 dBm P/sub out/ at peak PAE, respectively. The power gains at peak PAE for C-E and C-B mode operation are 6.1 dB and 7.1 dB, respectively. A 20-finger C-B HBT is capable of delivering 28.45 dBm (700 mW) of RF output power with 25% associated PAE. The peak PAE achieved with 20-finger C-B HBT is 32% with concurrent output power of 27.4 dBm. These represent the state-of-the-art power performance of SiGe-based HBTs. The performance difference between the common-emitter mode and the common-base mode has been analyzed.