Investigation of carrier localization in InAs/AlSb type-II superlattice material system

Abstract

We investigate carrier localization in the InAs/AlSb type-II superlattice (T2SL) material system using temperature- and excitation power (Iex)-dependent photoluminescence (PL). Evidence of carrier localization in T2SLs was observed by an S-shaped temperature dependence of the PL peak position. Analysis of the Iex-dependent PL at various temperatures also shows the existence of carrier localization in the T2SLs. The thermal activation energies in T2SLs were extracted to identify the nonradiative recombination mechanisms and the possible origins of localized states. We found that there are two thermal activation energies, E1 = 8.2–1.2 meV and E2 = ∼60 meV at various Iex. We interpret E1 as a thermal activation energy that comes from Anderson localization, associated with roughness due to As2 diffusion into the interfaces. This is because the extracted E1 values are comparable to the exciton binding energy of localization in various quantum structures. Carrier trapping at a state in the InSb interfacial layer (Tamm state) may account for the origin of E2. Based on previous reports, we believe that the 60 meV state might be a Tamm state if we consider thickness variations in the InSb interfacial layer for the T2SLs.

Interfacial Characteristics and Optical Properties of InAs/InAsSb Type II Superlattices for the Mid‐Infrared Operation

“…For superlattice systems, c close to 2/3 indicates Auger recombination and c close to 2 indicates Shockley-Read-Hall recombination. [32,33] The fitting results are shown in the inset of Figure 4a. The fitting constant c of the integrated intensity of the PL spectrum and the excitation power was 0.91, indicating that radiative recombination plays a dominant role.…”

On the origin of carrier localization in AlInAsSb digital alloy

“…Photoluminescence (PL) spectroscopy is a straightforward approach to evaluate localized states in heterogeneous systems. [12,13] In the presence of any localized state in heterogeneous, the PL peak emission energy will display S- [14] or V-shape [15] temperature dependency, which is contradictory with the behavior of a semiconductor band gap anticipated by the Varshni formula. [16] Carrier localization has been observed with PL in superlattices such as InAs/GaSb, [17] InAs/InAsSb, [18] InAs/AlSb, [12] and InAsSb/InSb.…”

“…[12,13] In the presence of any localized state in heterogeneous, the PL peak emission energy will display S- [14] or V-shape [15] temperature dependency, which is contradictory with the behavior of a semiconductor band gap anticipated by the Varshni formula. [16] Carrier localization has been observed with PL in superlattices such as InAs/GaSb, [17] InAs/InAsSb, [18] InAs/AlSb, [12] and InAsSb/InSb. [19] In this work, we employ temperature-dependent PL spectra to examine the impacts of interfaces in AlInAsSb digital alloy samples grown by molecular beam epitaxy for different periods.…”

“…The lowtemperature activation energy E 2 is likely to originate from a local state associated with the roughness of the interface as the E 2 values (6.72 meV and 3.76 meV) for both samples are comparable to the exciton binding energy in several quantum structure systems. [12,34,35] Figure 2 reveals that sample B has better crystal quality, suggesting that increasing the thickness of the interfacial layer generates a more uniform interface and reduces interfacial roughness. Furthermore, InSb-like interfaces have been proven to exhibit smoother interfacial and fewer point defects than AlAs-like interfaces in InAs/AlSb quantum wells and superlattices.…”

“…The photogenerated carriers are trapped in the energy states created by the InSb hole well, which are decoupled from the valence band of AlInAsSb digital alloy. [12] Indeed, this energy state at the InSb-like interface is known as the Tamm state. [39,40] According to the calculation result of Shen et al, [41] the value of the Tamm state is proportional to the thickness of the InSb-like interface.…”