Effect of Interfacial Schemes on the Optical and Structural Properties of InAs/GaSb Type-II Superlattices.

ABSTRACT

Incorporating an intentional strain compensating InSb interface (IF) layer in InAs/GaSb type-II superlattices (T2SLs) enhances device performance. But there is a lack of studies that correlate this approach's optical and structural quality, so the mechanisms by which this improvement is achieved remain unclear. One critical issue in increasing the performance of InAs/GaSb T2SLs arises from the lattice mismatch between InAs and GaSb, leading to interfacial strain in the structure. Not only that but also, since each side of the InAs/GaSb heterosystem does not have common atoms, there is a possibility of atomic intermixing at the IFs. To address such issues, an intentional InSb interfacial layer is commonly introduced at the InAs-on-GaSb and GaSb-on-InAs IFs to compensate for the strain and the chemical mismatches. In this report, we investigate InAs/GaSb T2SLs with (Sample A) and without (Sample B) InSb IF layers emitting in the mid-wavelength infrared (MWIR) through photoluminescence (PL) and band structure simulations. The PL studies indicate that the maximum PL intensity of Sample A is 1.6 times stronger than that of Sample B. This could be attributed to the effect of migration-enhanced epitaxy (MEE) growth mode. Band structure simulations understand the impact of atomic intermixing and segregation at T2SL IFs on the bandgap energy and PL intensity. It is observed that atomic intermixing at the IFs changes the bandgap energy and significantly affects the wave function overlap and the optical property of the samples. Transmission electron microscopy (TEM) measurements reveal that the T2SL IFs in Sample A are very rough compared to sharp IFs in Sample B, indicating a high possibility of atomic intermixing and segregation. Based on these results, it is believed that high-quality heterostructure could be achieved by controlling the IFs to enhance its structural and compositional homogeneities and the optical properties of the T2SLs.