Electrical and optical performances with extracted minority carrier lifetimes of InAs/GaSb SL photodetector operating in the mid wavelength infrared range
Introduction
InAs/GaSb based type-II superlattice photodetectors have been rapid progress over more than a decade [1], [2]. 6.1 A material family based on III-V material system enables new design of type-II superlattice (T2SL) photodetectors to be used in infrared applications [3]. The major advantage for T2SL detectors, compared to quantum well infrared photodetectors (QWIPs), has a direct bandgap and strong absorption for normal incidence of light like HgCdTe detectors. This results in a higher quantum efficiency which is important for camera applications with higher integration time. Since III-V material system has much strong chemical bonds, it has high thermal stability and compositional uniformity over large areas compared to HgCdTe material system. For these features, InAs/GaSb T2SL detectors are considered as an alternative candidate to HgCdTe and QWIPs for third generation imaging systems [4]. Band alignment of type-II superlattice has broken-gap such that the conduction band of the InAs layer is lower than the valence band of GaSb layer, as shown in Fig. 1. In the T2SL, the electrons are mainly localzed in the InAs layers, whereas holes are confined in GaSb layers. The superlattice bandgap is realized by the formation of the electron miniband in the conduction band and hole miniband in valence band respectively. Due to spatial seperations of electrons (InAs layers) and holes (GaSb layers), optical transitions are performed by the overlap of electron-hole wavefunctions at InAs/GaSb interfaces. This suppresses Auger recombination mechanisms and thereby enhances carrier lifetime. By varying the thickness of constituent materials, the band gap of superlattice can be tailored over a wide spectral range between 3 and 30 μm which covers short-to-very long infrared wavelengths in the atmospheric window [5], [6]. Important progresses have been obtained by several research groups for InAs/GaSb T2SL on device characterization [7], [8] and focal plane array (FPA) [9], [10] performance in the MWIR.
On the other hand, SLS technology is still in progress for improvement of focal plane array performance having with low noise equvalent temperature difference (NETD) and dark current densities, and carrier transport is one of the issue for a device performance. Identification of current mechanisms and extracted carrier lifetimes at each operating temperatures are very important for understanding the transport mechanism and improving the detector performance.
In this paper we investigate short period InAs/GaSb T2SL pin diode in the MWIR. Effective bandgap of the T2SL is optained by SEPM. Optical performance are carried out using spectral response, QE and detectivity measurements. Current density–voltage (J–V) characteristics as a function of temperature (100–250 K) are performed under dark conditions. J–V curves are modelled by Shockley formula in order to identify the dominant dark current mechanism in each operating temperature range. Then we extracted minority carrier lifetimes of the MWIR SL photodiode.
Section snippets
Experimental details
The superlattice pin photodiode was grown by molecular beam epitaxy. First a 100 nm GaSb buffer layer is deposited on GaSb substrate followed by a 20 nm lattice matched Al(x)GaAs(y)Sb buffer layer. 1000 nm thick p-type GaSb: Be (p = 1 × 1017 cm−3) bottom contact is grown on the buffer layer. The p-i-n part consists of 90 periods of 9.5/11 MLs InAs/GaSb SL layers with GaSb: Be (p = 1 × 1017 cm−3) p-region, 60 periods of 9.5/11 MLs InAs/GaSb SL layers i-intrinsic region and 60 periods of
Results and discussion
Responsivity of the detector has been measured using calibrated blackbody source (Newport, Oriel 67,000), lock-in amplifier (SRS, SR830 DSP) and mechanical chopper (SRS, SR540) system. Fig. 4 shows responsivity spectrum of a single pixel photodetector using a calibrated blackbody source at 450 K. The device exhibits a 50% cut-off wavelength of 4.9 μm at 79 K. Peak responsivity of the device is measured as 1.2 A/W is observed at 4 μm in wavelength. Temperature dependence of the band gap energy
Conclusion
We report on the electrical and optical performans of short period InAs/GaSb based T2SL pin structure. The device gives 1.2 A/W optical response at 4 μm with a 50% cut-off wavelength of 4.9 μm. QE is calculated as 45% at 3 μm at 79 K. Band structure of T2SL such as bandgap energy is verified by SEPM. Temperature dependence of J-V characteristics are revealed that dark current density shows diffusion-limited behaviour at a temperature range 250–160 K, while at lower temperature range 160–100 K,
Acknowledgement
Y.Ergun and M. Hostut acknowledge the supports of Anadolu University (BAP Grant: 13005F108, 1508F600) and Akdeniz University (BAP Grant: FKA-2015-918) respectively.
References (16)
- et al.
Inf. Phys. Technol.
(2006) - et al.
Superlattices Microstr
(2016) - et al.
Inf. Phys. Technol.
(2011) - et al.
Opto-Electron. Rev.
(2006) - et al.
Opto−Electron. Rev.
(2014) - et al.
J. Appl. Phys.
(2009) - et al.
Appl. Phys. Lett.
(2012) - et al.
Appl. Phys. Lett.
(2012)
Cited by (2)
Emerging Type-II Superlattices of InAs/InAsSb and InAs/GaSb for Mid-Wavelength Infrared Photodetectors
2022, Advanced Photonics ResearchInterband optical absorption obtained by pseudopotential method for type-II InAs/GaSb SL photodetectors
2021, Journal of Physics D: Applied Physics