平台型 p-i-n砷化銦鎵光偵測器之製作與特性量測

Abstract

在本論文中，以三道光罩及化學蝕刻顯影的方式製作1.55um圓形平台型( mesa type),InP(p+)╱Ga0.47In0.53As(undoped)╱ InP(n+),雙異質接 面(double heterojunction) PIN光偵測器。並選擇性的使用容積比例H2 SO4：H2O2：H2O＝1：1：50混合溶液對圓形平台周圍的牆壁(mesa sidewall,Ga0.47In0.53As)做表面浸泡處理20秒，來比較表面處理對暗電 流大小的影響。以電漿輔助化學氣相沈積系統(Plasma-Enhanced CVD, PECVD)成長SiO2定義出光偵測器大小，並做為mesa sidewall的鈍化層( passivation)及絕緣層，以降低其表面暗電流及方便金屬蒸鍍。再以蒸鍍 、舉離(lift-off)及快速退火(RTA)的方式製作歐姆接觸。並比較四種不 同半徑大小的光偵測器，分析暗電流是來自表面(mesa sidewall,平台周 圍的牆壁）或是塊材(bulk，平台的圓柱區域)。以上述方式製作之光偵測 器特性：暗電流密度5.0×10-2~2.0×10-1A/cm2，暗電流主要來源為表面 電流。量子效率15％~2.2％。有經過表面處理的元件,其暗電流大小為沒 有經過表面處理的 倍。 In this study, we fabricated and characterized Ga0.47In0.53As p- i-n photodectors. Starting from InP/Ga0.47In0.53As/InP or InAlAs/Ga0.47In0.53As/InP lattice-matched double heterostructures, we designed and made various sized mesa pin detectors lithography, chemical etching, lift-off metalization, rapid-thermal annealing(RTA) process. Plasma-enhanced chemical vapor deposition(PECVD) SiO2 is patterned to define the size and shape of dectectors.Sections of samples were dipped into solution with H2SO4 : H2O2 : H2O=1 : 1 : 50 for 20 seconds to study the effect of mesa sidewall surface processing to the reduction of leakage current. A second SiO2 film is regrown as a passivation and isolation layer for the mesa sidewall intensionally to minimize the surface leakage current.Under 1.55 um lumination through optical fiber, the quantum efficiencies of such fabricated pin detectors are ranged from 2.2％ ~ 15％. The dark current of those detectors with extra surface processing is effectively reduced to one-third that of the mesa detectors with merely SiO2 passivation layer. The dark current is attributed mainly due to the surface leakage ccurrent.