Performance of InP/InGaAs HBTs with a Thin Highly N-Type Doped Layer in the Emitter-Base Heterojunction Vicinity

Kenji KURISHIMA  Minoru IDA  Norihide KASHIO  Yoshino K. FUKAI  

Publication
IEICE TRANSACTIONS on Electronics   Vol.E95-C   No.8   pp.1310-1316
Publication Date: 2012/08/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E95.C.1310
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Heterostructure Microelectronics with TWHM 2011)
Category: III-V High-Speed Devices and Circuits
Keyword: 
InP,  InGaAs,  HBT,  turn-on voltage,  

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Summary: 
This paper investigates the effects of n-type doping in the emitter-base heterojunction vicinity on the DC and high-frequency characteristics of InP/InGaAs heterojunction bipolar transistors (HBTs). The n-type doping is shown to be very effective for enhancing the tunneling-injection current from the emitter and thus for reducing the collector-current turn-on voltage. However, it is also revealed that an unnecessary increase in the doping level only degrades the current gain, especially in the low-current region. A higher doping level also increases the emitter junction capacitance. The optimized HBT structures with a 0.5-µm-wide emitter exhibit turn-on voltage as low as 0.78 V and current gain of around 80 at JC = 1 mA/µm2. They also provide a current-gain cutoff frequency, ft, of 280 GHz and a maximum oscillation frequency, fmax, of 385 GHz at VCE = 1 V and JC = 3 mA/µm2. These results indicate that the proposed HBTs are very useful for high-speed and low-power IC applications.