| 摘要: | 本研究在650 V加強型功率氮化鎵電晶體(HEMT)整合一組雙向的氮化鎵閘極二極體(Bidirectional Schottky P-GaN Gate Diode, BSPGD)，形成BSPGD-HEMT，其概念是在傳統的650 V加強型功率氮化鎵電晶體(Power AlGaN/GaN HEMT)之閘極端連接雙向的氮化鎵閘極二極體(SPGD)。氮化鎵閘極二極體(SPGD)元件之設計是將HEMT元件之閘極端與源極端連接作為陽極端(anode)，HEMT元件之汲極端則作為陰極端(cathode)，從而構成SPGD元件。SPGD，BSPGD與HEMT使用相同的HEMT元件製程流程與氮化鎵磊晶，因此可以進行積體化的設計。
研究中比較了三種元件的電氣特性，分別為Power HEMT、SPGD-Power HEMT (SPGD-HEMT)以及BSPGD-Power HEMT (BSPGD-HEMT)。相較於HEMT，SPGD-HEMT和BSPGD-HEMT之閘極漏電流(VGS = 10 V, VDS = 0 V)明顯降低約11倍，顯示在HEMT之閘極端加入SPGD元件有助於降低閘極漏電流。在轉換特性與輸出特性方面， SPGD-HEMT與BSPGD-HEMT的臨界電壓(VTH)提升約1 V，同時保持相近的最大汲極電流(ID,MAX)與導通電阻(RON)。另外，在汲極漏電流(IDSS)特性方面，在閘極關閉(VGS = -1 V)下，SPGD-HEMT的汲極漏電流偏大，主要原因是在汲極偏壓下，HEMT的原閘極處或p-GaN層，因為浮接會有電荷累積，使閘極電壓上升，故導致元件無法確實關閉。本研究進一步改良SPGD的接法，改用雙向BSPGD將HEMT之原閘極端的浮接可以有額外路徑接到地，避免原閘極端浮接問題，並改善SPGD-HEMT元件汲極漏電流之問題。
最後進行HEMT和BSPGD-HEMT兩種元件電容特性與動態導通電阻之分析。在電容特性方面，BSPGD-HEMT元件之輸入電容(CISS)與反向轉移電容(CRSS)均明顯降低，有助於減少元件切換損耗並提升切換速度。在動態導通電阻特性方面，HEMT、BSPGD-HEMT兩種元件之歸一化後動態導通電阻比值均保持相近，顯示在單一HEMT元件之閘極端加入雙向的SPGD元件，並不會造成元件之動態導通電阻上升。;This study proposes a 650 V enhancement-mode GaN transistor integrated with a bidirectional Schottky P-GaN gate diode (BSPGD). The concept involves connecting the gate terminal of a conventional 650 V enhancement-mode GaN transistor (HEMT) to the bidirectional SPGD (BSPGD). The SPGD is designed by connecting the gate and source terminals of the HEMT as the anode and the drain terminal as the cathode, thus forming the SPGD device. In the novel BSPGD-HEMT device, the source and drain terminals are the same as those of the original HEMT, while the gate terminal is formed by the terminals of the bidirectional BSPGD. Both the SPGD and HEMT are fabricated using the same device process and GaN epitaxy, enabling an integrated design.
The study compares the electrical characteristics of three devices: HEMT, SPGD-HEMT, and BSPGD-HEMT. Both SPGD-HEMT and BSPGD-HEMT show a significant reduction in gate leakage current (VGS = 10 V, VDS = 0 V) by about 11 times compared to HEMT, indicating that adding an SPGD to the gate terminal effectively reduces leakage. In terms of transfer and output characteristics, SPGD-HEMT and BSPGD-HEMT exhibit a roughly 1 V increase in threshold voltage (VTH) while maintaining similar maximum drain current (ID,MAX) and on-resistance (RON). For drain leakage (IDSS) characteristics, the SPGD-HEMT has a higher drain leakage current due to gate charging through the HEMT’s CGD and CGS capacitance under high drain bias. The BSPGD-HEMT uses a bidirectional SPGD at the HEMT gate terminal to improve the drain leakage current issue in the SPGD-HEMT.
Finally, the study analyzed the capacitance characteristics and dynamic on-resistance of HEMT and BSPGD-HEMT. BSPGD-HEMT shows a significant reduction in input capacitance (CISS) and reverse transfer capacitance (CRSS), which can decrease switching losses and improve switching speed. Regarding dynamic on-resistance, the normalized ratios for HEMT and BSPGD-HEMT remain similar, indicating that adding the bidirectional SPGD at the gate terminal of the HEMT doesn’t increase dynamic on-resistance. |
