Midwave infrared InSb n B n photodetector

Abstract

The first demonstration of InSb photodetector with nBn design is reported. The nBn structure, grown by molecular beam epitaxy (MBE) on InSb substrate, is built by using n-type InSb as absorber layer and InAlSb alloy as barrier layer. The nBn detector, showing cut-off wavelength of 5.4 µm at 77 K in photovoltaic mode, exhibits dark current density as low as 10 −9 A/cm 2 at −50 mV reverse bias, at least two decades lower than usual InSb photodiode.Introduction: InSb remains the most commonly used material for the fabrication of high-speed photodetectors operating in the midwave infrared (MWIR, 3-5 µm) spectral region. The pn junctions of InSb photodiodes are usually fabricated by impurity diffusion or ion implantation, and nowadays InSb large focal plane arrays in formats up to 2k × 2k with 15 µm pitch are commercially available [1]. The InSb devices have to be cooled to 77 K, and the performance begins to be significantly degraded at higher temperature of 90 K, which is undoubtedly a strong disadvantage for power consumption. To satisfy the well-known size, weight and power (SWaP) criteria and then increase autonomy, reduce system size and improve the reliability, it is necessary to enhance temperature operation without reducing performances. Recently, a new structure design, called nBn [2], was developed to reach the high-temperature operation by eliminating the bulk Shockley-Read-Hall generation-recombination (G-R) currents. The usual nBn design is made of an n-type absorber layer, a wide-bandgap barrier region followed by an n-type contact. The transport of electron majority carriers is then blocked by the barrier while hole minority carriers, created by the absorption of infrared radiation, can move across the device. This specific barrier detector architecture was successfully applied to InAsSb [3][4][5], InAs/GaSb superlattice [6,7], InAs/InAsSb superlattice [8] and HgCdTe [9] photodetectors. Consequently, nBn design is now considered as the quantum structure architecture suitable to achieve high operating temperature in the MWIR domain.In this Letter, we report the first results of InSb nBn detector using n-type InSb layer as absorber layer and strained wide-bandgap InAlSb layer as barrier layer.Experiment: The InSb nBn structure was grown by molecular beam epitaxy (MBE) on n-type (Te-doped) InSb (100)-oriented substrate using a Varian Gen II MBE reactor. Fig. 1 shows the schematic band diagram of the considered InSb/InAlSb/InSb nBn structure. It consists of a 400 nm Te-doped (∼4 × 10 16 cm −3 ) buffer layer followed by 1 µm-thick Te-doped absorption layer (∼1 × 10 16 cm −3 ), followed by 50 nm-thick non-intentionally doped InAlSb barrier layer and capped with a 200 nm Te-doped InSb layer (∼2 × 10 16 cm −3 ). 0 0.1 0.2 0.3 0.4 0.5 0.6 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 DE V1 DE V2 DE C1 In 0.85 Al 0.15 Sb InSb cap layer n-type n cap~2 x 10 16 cm -3 barrier layer non-intentionally doped (nid) InSb absorption layer n-type n abs~1 0 16 cm -3 V = 0 V T = 110 K energy, eV thickness, mm E F gradual composition ...

Understanding the $C-V$ Characteristics of InAsSb-Based nBn Infrared Detectors With N- and P-Type Barrier Layers Through Numerical Modeling

“…A higher doping density in the barrier layer results in a broadening of the C-V peak near zero bias for all thicknesses, implying a larger reverse or forward bias required to deplete the absorber and contact layers respectively. This is also consistent with (6). As the thickness of the barrier is increased, the barrier is no longer fully depleted.…”

“…When the AL and CL are highly doped, the results are comparable to the N-type case since the depletion capacitances are small in comparison to the barrier capacitance. The similarity of the figures is also due in part to the low crossover voltages given by (6); only a very small reverse or forward bias is required to fall into the same regime as the N-type case where one of the layers is depleted, while the other is accumulated.…”

“…They were also able to estimate the combined thickness of the barrier and contact layers through the forward biased C-V [5]. Evirgen et al used C-V profiling to characterize three separate InSb-based nBn photodetectors [6]. More recently, Rhiger et al characterized an nBn sample with a strained superlattice absorbing layer; they were able to determine an effective donor density in the absorber, and through the use of a witness metalinsulator-metal sample, the p-type doping density in the barrier layer [7].…”

Highly Sensitive InSb Nanosheets Infrared Photodetector Passivated by Ferroelectric Polymer

“…[10] As a direct bandgap III−V compound semiconductor, InSb has the smallest bandgap and highest electron mobility, making it the potential performing detector material in the middle wavelength infrared (MWIR) range. Due to these advantages, InSb has been widely used for infrared photodetectors, [34][35][36][37][38][39] whereas high dark current discourages the development of this narrow bandgap semiconductor as a photodetector. Using InSb nanostructured materials may be a good solution to overcome this drawback since phonon scattering is suppressed as the size decreases.…”

Ga-free InAs/InAsSb type-II superlattice (T2SL) photodetector for high operating temperature in the midwave infrared spectral domain

“…In addition, to compare the performances of our Ga-free XBn device, we have also plotted in Fig. 11 the data at bias operation of three different types of InSb-based photodetectors 16 (MWIR broadband detectors): -InSb pn junction fabricated by standard planar process, -InSb pin junction fabricated by MBE, -InSb nBn structure fabricated by MBE 17 . The black line in Fig.…”