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학술지 Anomalous Photocurrent Reversal Due to Hole Traps in AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes
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임승영, 김태수, 강재상, 김재선, 송민협, 김현덕, 송정훈
Micromachines, v.13 no.8, pp.1-10
22HB1200, 멀티밴드 신호전송을 위한 다중 광채널 발생/조형 기술 개발, 송민협
The trap states and defects near the active region in deep-ultraviolet (DUV) light-emitting diodes (LED) were investigated through wavelength-dependent photocurrent spectroscopy. We observed anomalous photocurrent reversal and its temporal recovery in AlGaN-based DUV LEDs as the wavelength of illuminating light varied from DUV to visible. The wavelength-dependent photocurrent measurements were performed on 265 nm-emitting DUV LEDs under zero-bias conditions. Sharp near-band-edge (~265 nm) absorption was observed in addition to broad (300??800 nm) visible-range absorption peaks in the photocurrent spectrum, while the current direction of these two peaks were opposite to each other. In addition, the current direction of the photocurrent in the visible wavelength range was reversed when a certain forward bias was applied. This bias-induced current reversal displayed a slow recovery time (~6 h) when the applied forward voltage was removed. Furthermore, the recovery time showed strong temperature dependency and was faster as the sample temperature increased. This result can be consistently explained by the presence of hole traps at the electron-blocking layer and the band bending caused by piezoelectric polarization fields. The activation energy of the defect state was calculated to be 279 meV using the temperature dependency of the recovery time.
KSP 제안 키워드
65 nm, Activation Energy, Anomalous photocurrent, Current direction, Current reversal, Forward voltage, Hole trap, Light-emitting diodes (leds), Photocurrent measurements, Photocurrent spectroscopy, Photocurrent spectrum
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