High Efficiency AlGaAs/GaAs Power HBTs at a Low Supply Voltage for Digital Cellular Phones

Teruyuki SHIMURA  Takeshi MIURA  Yutaka UNEME  Hirofumi NAKANO  Ryo HATTORI  Mutsuyuki OTSUBO  Kazutomi MORI  Akira INOUE  Noriyuki TANINO  

IEICE TRANSACTIONS on Electronics   Vol.E80-C   No.6   pp.740-745
Publication Date: 1997/06/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Microwave and Millimeterwave High-power Devices)
heterojunction bipolar transistor,  digital cellular phone,  individual thermal shunt,  emitter air-bridge,  bias mode,  

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We present a high performance AlGaAs/GaAs power HBT with very low thermal resistance for digital cellular phones. Device structure with emitter air-bridge is utilized and device layout is optimized to reduce thermal resistance based on three-dimensional thermal flow analysis, and in spite of a rather thick substrate (100 µm), which achieved a low thermal resistance of 23/W for a multi-finger (440 µm240 fingers) HBT. This 40 finger HBT achieved power added efficiency (PAE) of over 53%, 29.1 dBm output power (Pout) and high associated gain (Ga) of 13.5 dB with 50 kHz adjacent channel leakage power (Padj) of less than -48 dBc under a 948 MHz π/4-shifted QPSK modulation with 3.4 V emitter-collector voltage. We also investigated the difference of RF performance between two bias modes (constant base voltage and current), and found which mode is adequate for each stage in several stage power amplifier for the first time.