Linearity Improvement of InGaP/GaAs HBTs and Characterization of InP-based Type-I/II HBTs

• Main Authors: Che-ming Wang, 王則閔
• Other Authors: Yue-ming Hsin
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/9q3hpp

博士 === 國立中央大學 === 電機工程研究所 === 96 === Heterojunction Bipolar Transistors (HBTs) proposed to improve the emitter efficiency by base-emitter (BE) heterojunction in 1958s. The GaAs-based and InP-based HBTs were implemented as the material growth techniques of MOCVD and MBE became mature in 1980s. In recent, the HBTs are widly applicated in the power amplifier of wireless communication system. The nonlinear characteristic of HBTs is an important point that affects power performance of circuit design. The four major sources of HBTs nonlinearity and the large-signal swing related nonlinear factors are discussed. InP-based HBTs achieved record high speed results and are currently the most promising technologies for achieving Terahertz (THz) operation. The energy band and relation material of the type-I and type-II of InP-based HBTs are studied. And the correlation between cutoff frequency (fT), maximum oscillation frequency (fMAX), collector thickness, breakdown voltage, collector current density is compared and analyzed. In the chapter 2, a non-uniform collector doping design is studied by employing a thin high-doping layer inside the low doping collector. The collector doping design limits collector depletion and electric field at the thin-high doping layer. The ratio of maximum to minimum values of CBC with uniform and non-uniform collector doping are 1.6 and 1.1. This collector design results in the re-distribution of the electric fields in the collector to delay the onset of Kirk effect and thus improve the current handling capability, fT, output power, and linearity characteristics. In the chapter 3, a non-uniform collector doping design of GaAs HBTs by employing a thin high-doping layer inside the low doping collector are fabricated and analyzed. The identical emitter and base epi-layer structures shows the similar results in dc characteristics except the negligible reduction in breakdown voltage. The fT of non-uniform collector increases 12 GHz compared to convention HBT (HBT-A) by delay onset of Kirk effect. The power performance and linearity characteristic show the improvement of 2.2 dB in saturation output power and 10 dB in OIP3 at frequency 1.8 GHz. The HBTs (HBT-B and HBT-C) with a thin high-doping layer in the collector demonstrate the improved cutoff frequency, linearity and output power characteristics compared with a conventional HBT. In the chapter 4, a submicrometer 0.6×12 μm2 InP/InGaAs DHBTs by E-bean lithography is fabricated and measured. The current gain is 28.4 at JC = 666 kA/cm and the common-emitter breakdown voltage exceeds 5 V. The fT and fMAX of the InP/InGaAs DHBT are 230 GHz and 135 GHz, respectively. The saturation output power of 14.3 dBm and the maximum output power density of 3.7 mW/µm2 are measured at Ka-band with load-pull system matching to maximize the output power. This is the highest output power density obtained with submicrometer DHBTs at 29 GHz every reported for on-wafer load-pull measurement using InP/InGaAs DHBT technology. Finally, in the chapter 5, the InAlAs-InP composite emitter could effectively reduce electron pile-up at the InP/GaAsSb base-emitter junction and improve current gain. The current gain (