Low-Dark-Current Heterojunction Phototransistors with Long-Term Stable Passivation Induced by Neutralized (NH4)2S Treatment

概要

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To investigate the effects of surface leakage on the temperature-dependent dark and optical performance of a heterojunction phototransistor (HPT), three sets of HPTs were prepared. They were unpassivated (HPT A), passivated with diluted (NH4)2S (HPT B), and passivated with neutralized (NH4)2S (HPT C). Passivation treatment successfully suppresses surface-defect-induced effects. The passivated HPTs exhibit a reduced dark current and an enhanced signal-to-noise ratio (SNR). HPT A exhibits a room-temperature collector dark current ($I_{\text{Cdark}}$) of 0.59 nA at a $V_{\text{CE}}$ of 1 V, while those of HPTs B and C are 0.03 and 0.89 pA, respectively. The room-temperature SNR values for HPTs A, B, and C at a $P_{\text{in}}$ of 8.3 (107.6) nW are 5.9 (42), 59 (91), and 91 (122) dB, respectively. After a three-week air exposure, the room-temperature SNR at a $P_{\text{in}}$ of 107.6 nW decreases to 25 (67) dB for HPT A (B), while it is 116 dB for HPT C. The decrease for HPT C is only 6 dB. A long-term stable passivation with good thermal stability has been achieved by neutralized (NH4)2S treatment.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2008-01-25