THz輻射偵測用砷離子佈植砷化鎵偶極天線之研製

Abstract

本論文在探討多重砷離子佈植(50、100、200Kev，1016 ions/cm2)砷化鎵薄膜材料，經過爐管退火製程600℃，時間分別長達30分鐘以及60分鐘，以此基版所製造之偶極天線在次毫米波偵測上的特性。 由於次毫米波的電場屬於低電場源，所以，金屬與半導體間的接面特性，影響THz輻射的偵測結果 ; 在暗電流量測結果中可發現，退火長達60分鐘的多重砷離子佈植砷化鎵基板以及半絕緣性砷化鎵基板有明顯的蕭特基能障，此從退火60分鐘砷離子佈植砷化鎵在53V有電流遽增,及半絕緣性砷化鎵在36V有電流遽增等處來判定 ; 而對於退火30分鐘的多重砷離子佈植砷化鎵而言，金屬與半導體間則具有良好的歐姆接面，將三種基材製造的偶極天線，用於我們所架設的光導取樣系統作為偵測器，其中只有退火30分鐘的多重砷離子佈植砷化鎵的訊號夠大而偵測到THz輻射波，依此判斷應與歐姆接面的存在有關。 THz 輻射源,主要有兩種來源產生，一為光導天線，另一為非線性晶體的光整流特性所產生。在我們所架設的光導取樣系統中，很明顯地，光整流效應的頻寬(1.5THz)大於光導天線所產生THz輻射的頻寬(0.5THz) ，同時亦證明此光導取樣系統在130飛秒的激發脈衝下已達到系統極限。 最後，我們同時比較低溫成長砷化鎵，多重砷離子佈植砷化鎵,與半絕緣性砷化鎵在THz 輻射偵測上的差異，可發現多重砷離子佈植砷化鎵在訊噪比 (~100)上比低溫長成砷化鎵(~10000)低兩個數量級，而比半絕緣性砷化鎵(~20)大五倍。在偵測方面,以10um<110>銻化鋅為發射源，低溫長成砷化鎵偵測器可達40THz，而多重砷離子佈植砷化鎵可達30THz，而半絕性砷化鎵則只達到20 THz ; 由於多重佈植砷化鎵在製程上比低溫長成砷化鎵更經濟,而且在偵測輻射波形上與低溫長成偵測的頗有雷同，因此在次毫米波偵測應用上具有相當淺力。

We study the multi-arsenic-implanted GaAs (50、100、200Kev，1016 ions/cm2) after furnace annealing for 30 minutes and 60 minutes at 600℃, used as the substrates of dipole antennas to detect THz radiation. Since the electric field, biased by THz radiation and belongs to the low electric field, the contact between the metal and semiconductor plays an important role. According to the current surge occurs at the 53V and 36V in the multi-GaAs: As+ after annealing 60 minutes and SI GaAs, respectively. The Schottky barrier occurs in the multi-GaAs: As+ after annealing 60 minutes and semi-insulating GaAs. However, the contact between the metal and semiconductor, which is GaAs: As+ after annealing 30 minutes, is ohmic contact. And then, the THz radiation is detected by the detector based on GaAs: As+ after annealing 30 minutes. Generally speaking, the THz emitter is photoconductive antennas or electro-optical crystals. THz radiation measured from the photoconductive sampling system built by us can be differentiated from the two kinds of emitters. Observably, the spectrum of THz radiation, which is 1.5THz, generated from optical rectification is broader than that of photoconductive antennas, which is about 0.5THz. And it is demonstrated that the optical setup reaches the limit of the system as the exciting pulse width is 130fs. Finally, the photoconductive dipole antennas based on SI GaAs, LT-GaAs, and multi-GaAs: As+ are compared on the THz waveforms and the Fourier transformed spectrums. It is observed that the SN ratio of multi-GaAs: As+ (~100) is lower than that of LT-GaAs (10000), but larger than SI GaAs (~20) about five tomes. In detection, the spectrum detected by LT-GaAs-based dipole antenna is 40THz as the 10um<110> ZnTe is emitter. At the same situation, the spectrum detector by multi-GaAs: As+-based and SI-GaAs-based dipole antennas are 30 THz and 20THz, respectively. Since the process of preparation for multi-GaAs: As+ is easier than LT-GaAs and the detected THz waveform is similar to that detected by LT-GaAs, multi-GaAs: As+ may be the anticipated photoconductor in THz detection.