Passivation Study of InAs/GaSb Type-II Strained Layer Superlattice in Mid-wave Infrared Photodetector
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Passivation Study of InAs/GaSb Type-II Strained Layer Superlattice in Mid-wave Infrared Photodetector Ha Sul Kim∗ Department of Physics, Chonnam National University, Kwangju 61186, Korea (Received 4 August 2020; revised 22 September 2020; accepted 23 September 2020) This paper reports the results of a passivation study of InAs/GaSb type-II strained layer superlattice for a mid-wave infrared detector with p-on-n polarity. The cutoff wavelength of the fabricated photodiode was observed to be 5.5 μm at 77 K. At a negative bias of 0.1 V, the dark current density was measured to be 2.8 × 10−5 , 8.2 × 10−5 , and 3.1 × 10−2 A/cm2 for the diodes passivated with SiO2 and Si3 N4 and the unpassivated diode, respectively. The photodiode passivated with SiO2 demonstrated a reduction in dark current density of approximately three times than that of the diode passivated with Si3 N4 . Therefore, the dynamic resistance-area product of the photodiode under the negative bias, passivated with SiO2 , showed a larger value than that of the device passivated with Si3 N4 . In contrast, at 100–150 K, the resistance-area product at the zero-bias voltage of the photodiode passivated with Si3 N4 showed a higher value than that of the device passivated with SiO2 . It is believed that the relatively low thermal stress between GaSb and Si3 N4 reduced the dark current density at zero bias and increased R0 A in this temperature range. Keywords: Infrared photodiode, InAs/GaSb, Strained layer superlattice DOI: 10.3938/jkps.77.714
I. INTRODUCTION Recently, infrared (IR) sensors have been used in various fields owing to their wide range of applications in the detection of infectious viruses, industrial automation, and space exploration. HgCdTe or InSb materials are used in cooling thermal imagers operated at cryogenic temperatures to reduce the noise from various sources in a photodetector. However, HgCdTe materials cause environmental pollution due to the use of Hg or Cd, and achieving a uniform ingredient combination for a full wafer is difficult during material growth. Furthermore, the fixed band of InSb limits the development of wavelength-tunable IR detectors required by third-generation IR detectors [1]. Alternatively, the InAs/GaSb type-II strained layer superlattice (T2 SLS) can sense a wide range of IR wavelengths from 3 to 30 μm depending on the thickness of InAs and GaSb [2]. In recent years, studies have been conducted on the material growth and device structure for T2 SLS. The results are promising for the development of next-generation IRsensing systems [3,4]. A mesa structure should be fabricated using a wet or dry etching process to operate a grown wafer as a photodiode. Subsequently, a semiconductor is abruptly terminated at the end of the mesa, prompting the peri∗ E-mail:
odic structure of the semiconductor to end suddenly at the mesa surface and device sidewall to become oxidized. In addition, the deposition of foreign substances on the mesa surface during the subsequent fabrication process is initiated [5]. Then, an unfavorable
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