| 摘要: | 摘 要 無線通訊系統中，功率放大器在收發模組中佔了相當重要的地位;而功率放大器的飽和輸出功率與附加功率效益(PAE)的要求愈來愈嚴格。對功率放大器的應用要求而言，決定功率與附加功率效益的主要原因莫過於元件本身，而目前的微波元件中以HBT的使用最普遍。 本論文主要針對磷化銦鎵/砷化鎵雙載子電晶體(InGaP/GaAs HBT)做結構上的設計，此結構上的設計主要針對集極(collector)材料的設計，設計出三種不同集極結構的HBT。此三種不同集極結構的HBT分別是SHBT (Single Heterojunction Bipolar Transistor)，DHBT (Double Heterojunction Bipolar Transistor)，CHBT (Heterojunction Bipolar Transistor with Composite collector )。設計CHBT的目的是要在SHBT與DHBT的特性之間做取捨，並依功率放大器的應用要求來決定。 所製作完成的大尺寸HBT(AE = 80 × 80 μm2)，在JC = 1kA/cm2偏壓下，SHBT的電流增益為92，而崩潰電壓(BVCEO) 為8.15 V，VCE,offset為0.1 V；在相同的偏壓下，CHBT的電流增益為83，而崩潰電壓(BVCEO)達16.5 V，VCE,offset為0.075 V；在相同的偏壓下，DHBT的電流增益為79，崩潰電壓(BVCEO) 為21 V，VCE,offset為0.075 V。因為結構上的設計主要針對集極(collector)材料的設計，所以電流增益變化不大，但是DHBT所能夠得到的崩潰電壓與VCE,offset之改善皆在CHBT上獲得相同的驗證。 不同集極結構的HBT元件(AE = 3 × 12 μm2)高頻特性量測結果在VC = 3V，JC =30kA/cm2偏壓下，SHBT截止頻率(fT)達46 GHz，最大震盪頻率(fmax)達30 GHz；CHBT截止頻率(fT)達36 GHz，最大震盪頻率(fmax)達20 GHz；DHBT截止頻率(fT)達36 GHz，最大震盪頻率(fmax)達21 GHz。三種結構仍以SHBT為佳，DHBT與CHBT的基集接面仍受到在高電流時DEC的影響。而元件功率特性是以尺寸為 4 × 12μm2的元件進行量測，當操作頻率在1.8 GHz下，VC = 3.6 V，IC = 15 mA時，SHBT的線性功率增益(G0)為19.7dB，最大輸出功率(Pout,max)為14 dBm，最大附加功率增益(PAE,max)為39.2 %；CHBT的線性功率增益(G0)為16.9 dB，最大輸出功率(Pout,max)為13.2 dBm，最大附加功率增益(PAE,max)為31.3 %；DHBT的線性功率增益(G0)為17.1 dB，最大輸出功率(Pout,max)為11.4 dBm，最大附加功率增益(PAE,max)為28.6 %。從研究結果發現集極設計的不同所表現出來的特性也不同，而功率量測結果，顯示了CHBT的低VCE,offset與on-resistance確時能有效的改善功率特性。 Abstract In wireless communication systems，power amplifiers play a important role in transmit-receive module；Power amplifiers require high saturation output power and high power-added efficiency(PAE)。However，the power and power-added efficiency of power amplifiers is determined by device performance，at present，the HBT used generally in microwave device。 This paper focus on InGaP/GaAs bipolar transistor(InGaP/GaAs HBT) with a novel collector design，three different structures in collector are SHBT (Single Heterojunction Bipolar Transistor)，DHBT (Double Heterojunction Bipolar Transistor)，CHBT (Heterojunction Bipolar Transistor with Composite collector )。The purpose of design CHBT is tradeoff between SHBT and DHBT characteristics。 We fabricate large area HBT(AE = 80×80 μm2)，at JC = 1kA/cm2，SHBT’s current gain is 92，breakdown voltage(BVCEO) is 8.15V，VCE,offset is 0.1V；at the same JC，CHBT’s current gain is 83，breakdown voltage (BVCEO) is 16.5V，VCE,offset is 0.075V；at the same JC，DHBT’s current gain is 79，breakdown voltage (BVCEO) is 21V，VCE,offset is 0.075V。Because we focus on collector design，the variation of current gain is small，CHBT can obtains both the improvement of breakdown voltage and VCE,offset。 Three different structure in collector HBT’s (AE = 3×12μm2) high frequency performance，at VC = 3V，JC =30kA/cm2，SHBT’s cut-off frequency(fT) is 46GHz，maximum oscillation frequency(fmax) is 30GHz；CHBT’s cut-off frequency(fT) is 36GHz，maximum oscillation frequency(fmax) is 20GHz；DHBT’s cut-off frequency(fT) is 36GHz，maximum oscillation frequency(fmax) is 21GHz。The results，SHBT is the best，DHBT and CHBT BC junction are still influenced by DEC at high current density。Three different structure in collector HBT’s (AE = 4×12 μm2) power performance，operated frequency is 1.8GHz，at VC = 3.6 V，IC = 15 mA，SHBT’s linear power gain(G0) is 19.7dB，maximum output power(Pout,max) is 14dBm，maximum power-added efficiency(PAE,max) is 39.2 %；CHBT’s linear power gain(G0) is 16.9dB，maximum output power(Pout,max) is 13.2dBm，maximum power-added efficiency(PAE,max) is 31.3 %；DHBT’s linear power gain(G0) is 17.1dB，maximum output power(Pout,max) is 11.4dBm，maximum power-added efficiency(PAE,max) is 28.6 %。According to the results of measurement，we find the different structures in collector are also different performance，at the results of power perfomance，CHBT can improve power performance effectively due to lower VCE,offset and on-resistance。 |
