本論文以氮化鎵(GaN)高電子遷移率電晶體(HEMT)進行元件低頻雜訊特性與應用於Sub-6 GHz單晶片微波積體電路(MMIC)功率放大器研究。透過雜訊功率頻譜密度(power spectral density)的方式將二種氮化鎵元件(有/無p-GaN閘極層)操作於線性區進行低頻雜訊的量測，探討出元件的閃爍雜訊(flicker noise)由carrier number fluctuation機制所主導。並推導出p型氮化鎵閘極元件可能由於p-GaN閘極層的鎂向外擴散至AlGaN能障層與GaN通道層，在AlGaN/GaN介面處有相對無p-GaN閘極層有較高的缺陷密度。同時發現成長於SiC基板上之商用氮化鎵高頻元件(無p-GaN閘極層)在低頻區域下除了閃爍雜訊之外也存在產生-再結合雜訊(generation-recombination noise: g-r noise)。利用不同環境溫度測量，使用阿瑞尼斯圖的方式分析g-r noise的缺陷位置，得到位於導通帶之下0.35 ~ 0.53 eV缺陷。 另外藉由商用氮化鎵高電子遷移率電晶體製程技術設計一應用於5G通訊系統Sub-6 GHz頻段之MMIC Doherty功率放大器，測量出Doherty功率放大器操作於3.5 GHz時其輸出功率增益達11.6 dB，1-dB功率壓縮點(OP1dB)為26.9 dBm，最大輸出功率(PSAT)達33.2 dBm，功率附加效率(PAE)為24.4 %。此外，透過64-QAM正交幅度調變的數位調變訊號觀察當向量誤差失真(EVM) < -25 dB時其平均輸出功率最高可達27.7 dBm，且其鄰近通道功率比例(ACPR)為-29.7 dBc。 ;In this study, gallium nitride (GaN) high electron mobility transistor (HEMT) low-frequency noise characteristics and monolithic microwave integrated circuit (MMIC) power amplifier at Sub-6 GHz application are presented. Noise power spectral density (PSD) of two types of devices (with/without p-GaN gate layer) have been characterized in linear region by using low-frequency noise measurement, demonstrating that flicker noise of devices are dominated by carrier number fluctuation. Also, derived that devices with p-GaN gate layer show higher trap density at AlGaN/GaN interface probably due to magnesium(Mg) out-diffusing into AlGaN barrier and GaN channel. Meanwhile, devices which fabricated on SiC substrate (without p-GaN gate layer) RF devices in low-frequency region not only 1/f noise exists also accompany by generation-recombination noise (g-r noise) has been observed. In this case, devices measured at various temperature, using Arrhenius plot extracted that g-r noise originated from a trap level with 0.35 ~ 0.53 eV below conduction band. MMIC Doherty power amplifier (DPA) operating at Sub-6 GHz for 5G communication system applications were designed based on commercial GaN HEMT process. The measured DPA exhibits power gain of 11.6 dB, 1-dB compression point (OP1dB) of 26.9 dBm, a saturated output power (PSAT) of 33.2 dBm, and a power added efficiency (PAE) of 24.4% at 3.5 GHz. Moreover, DPA can deliver maximum average power of 27.7 dBm with error vector magnitude (EVM) < -25 dB for 64-quadrature amplitude modulation (QAM) signals and adjacent channel power ratio (ACPR) of -29.7 dBc.
