單一與多重佈值砷離子砷化鎵光導元件之研究

Abstract

本論文主要探討相同佈值濃度下，單次砷離子佈值（200Kev，1016ions/cm2)，和多次砷離子佈植（50、100、200Kev，1016ions/cm2)砷化鎵材料，經過爐管退火製程600℃，30分鐘之後所製作光導元件特性。 在暗電流方面的比較，單一佈值砷離子砷化鎵和多重佈值砷離子砷化鎵材料，經過600℃、30min的退火製程，其暗電流比原先未經過退火製程，驟降四個數量級以上，在定壓10V時，間距100μm的簡單光導量測暗電流，未退火單一佈植砷化鎵暗電流為3×10-4A，未退火多重佈值砷化鎵暗電流為4×10-4A；退火後單一佈植砷化鎵暗電流為3.65×10-8A，退火後的多重佈植砷化鎵暗電流為2×10-8A。 時域響應量測方面，經過外部電光取樣系統的量測得知，由於多次佈植砷離子砷化鎵薄膜的佈植濃度分佈比單次佈植的濃度分佈均勻外，多重佈值所佈值的砷離子數，亦為單一佈值次數的三倍，所以在加高偏壓的工作環境中，似乎其回復時間(falltime)比單次佈植砷離子砷化鎵來的快，且高偏壓下所造成的尾部影響(tail effect)，單一佈值砷化鎵的尾部效應，有隨著偏壓增高而明顯變大的趨勢，在偏壓60V時，其尾部的高度幾乎為光電流峰值的50﹪左右，但同樣在偏壓60V，多重佈值砷化鎵的尾部高度仍可以維持在光電流峰值的15﹪以內，抑制尾部效應確實比單一佈值砷化鎵來的佳；600℃、30分鐘的爐管退火製程使得1016ions/cm2劑量砷離子佈值砷化鎵製作的共面微條形光導開關(CPS)，具有約2.5ps左右的時域響應，上升時間(risetime)皆為1.2ps，則不因佈植次數而有顯著的變化。 綜合歸納單次和多次砷離子佈植砷化鎵薄膜，可以發現多次砷離子佈值砷化鎵，經過600℃、30分鐘的爐管退火製程後，有較佳的抑制尾部效應(tail effect)，可操作在更高的電場(40KV/cm)以上，訊號仍有良好訊噪比，整體比較起來，確實比單一佈值砷化鎵材料有較佳的特性。

We have studied the characteristics of photoconductive devices fabricated on single-dose and multi-dose Arsenic-ion-implanted GaAs, the single-dose sample were implanted with 200keV, and the multi-dose sample were implanted with 50,100 and 200keV, arsenic ions at 1016 ions/cm2 and furnace annealed at 600℃,30 min. The annealing process reduces the dark currents of the GaAs:As+, even lower than S.I.; at the voltage is 10V, the dark current of annealed single-dose Arsenic-ion-implanted GaAs is 3.65×10-8 A, the dark current of annealed multi-dose Arsenic-ion-implanted GaAs is 2.03×10-8 A, the dark current of S.I. GaAs is 9.57×10-8 A, because of As precipitates was present and the implanted region layer was recrystalized. By using a passive-mode-locked Ti:Sapphire laser (□=0.81□m) generating 150fs optical pulses, in an external electro-optic sampling system with a 60□m electro-optic probe, we found the temporal response of CPS devices fabricated with furnace-annealled single-dose As-implanted GaAs with 1016cm-2 arsenic ions, the full width at half maximum(FWHM) are 2.26ps, 2.89ps, 3.05ps, and 3.22ps for bias voltage are 30V, 40V, 50V and 60V, respectively. For single-dose As-implanted GaAs device, the tail amplitude seems grow as the dc bias was increased . In order to reduce the tail effect and leakage current, multiple ion dosage with various implantation energies have been implemented. The temporal response of CPS devices fabricated with furnace-annealled multiple-dose As-implanted GaAs with 1016cm-2 arsenic ions, the full width at half maximum(FWHM) are 2.37ps, 2.77ps, 2.63ps, and 2.85ps for bias voltage are 30V, 40V, 50V and 60V, respectively. We have demonstrated that the furnace-annealled multiple-dose As-implanted GaAs CPS device, better performance was achieved with single-dose As-implanted samples. The devices of the multiple-dose As-implanted GaAs sample exhibit a responsivity of 0.002A/W at 100mW, dark current of 9.22□10-7A at 40V and well persistent tail effect response .