P-HEMT 在CDMA通訊系統上線性之製作與研究

Abstract

在本研究過程中，我們已經成功地設計並發展出高電子遷移率電晶體的製程。整個過程從製作FET的最基本步驟：元件隔離、歐姆接點、閘極製作著手，另外也使用了較新的製程技術，如：電鍍、空橋架設，整合這些製程，順利地完成高電子遷移率電晶體的製作。在量測方面，我們比較了Single Delta doping和Double Delta doping在直流、小訊號、大訊號方面的表現。元件在300K下的直流特性，Single Delta doping的Idss=152mA/mm，最高gm=244mS/mm，而Double Delta doping的Idss=260mA/mm，最高gm=247mS/mm；高頻小訊號特性上，Single Delta doping的fT=14GHz、fmax=40GHz，Double Delta doping的fT=16~17GHz、fmax=50GHz；高頻大訊號特性上，Single Delta doping的功率增益效益為32％、Double Delta doping的功率增益效益為37％，Single Delta doping的P1dB點為-2.59dBm、Double Delta doping的P1dB點為0.74dBm；Single Delta doping的OIP3=26.91dBm、Double Delta doping的OIP3=27.65dBm。在CDMA系統之應用上，我們針對Single 和 Double delta doping這兩種結構量測其ACPR值，發現Double delta doping 結構的ACPR值要比Single delta doping的ACPR值來的好。因此，綜合上所述我們可以知道在線性的應用上Double delta doping要比Single delta doping為佳。此外，本論文為第一次發表針對Double delta doping 和Single delta doping這兩種不同的結構在CDMA通訊系統上的線性應用比較，且也獲得不錯的結果。

In this study , we have developed the processing techniques for GaAs psedomorphic HEMT. The process starts with the three basic fabrication steps used in general FET processing. These include mesa etching, ohmic contact formation and gate formation. We have also successfully developed two specific process steps: electroplating and airbridge setting. In our measurement, we compare the performance of single delta doping structure and double delta doping structure in DC、small signal and large signal. At 300K,the gm and Idss of single delta doping structure were 244mS/mm and 152mA/mm, respectively. For double delta doping structure, the gm and Idss of single delta doping structure were 247mS/mm and 260mA/mm, respectively. In small signal measurement, the fT and fmax of single delta doping structure were 14GHz and 40GHz, respectively. For double delta doping structure, the fT and fmax were 16~17GHz and 50GHz, respectively. In large signal measurement, the power addition efficiency、P1dB and OIP3 of single delta doping structure were 32%、2.59dBm and 26.91dBm, respectively. For double delta doping structure, the power addition efficiency、P1dB and OIP3 were 37%、0.74dBm and 27.65dBm. For the application in CDMA communication system, we have measured the adjacent channel power leakage ratio (ACPR) of single and double delta doping structure. We found that the ACPR of double delta doping structure were better than single delta doping structure. According to above, we knew that for the linearity application double delta doping structure are more suitable than single delta doping structure. Besides, this is the first time to compare the linearity in CDMA communication of single and double delta doping structure and we have got a good experimental result.