Optical properties of InAsBi and optimal designs of lattice-matched and strain-balanced III-V semiconductor superlattices

Abstract

The optical properties of bulk InAs0.936Bi0.064 grown by molecular beam epitaxy on a (100)-oriented GaSb substrate are measured using spectroscopic ellipsometry. The index of refraction and absorption coefficient are measured over photon energies ranging from 44 meV to 4.4 eV and are used to identify the room temperature bandgap energy of bulk InAs0.936Bi0.064 as 60.6 meV. The bandgap of InAsBi is expressed as a function of Bi mole fraction using the band anticrossing model and a characteristic coupling strength of 1.529 eV between the Bi impurity state and the InAs valence band. These results are programmed into a software tool that calculates the miniband structure of semiconductor superlattices and identifies optimal designs in terms of maximizing the electron-hole wavefunction overlap as a function of transition energy. These functionalities are demonstrated by mapping the design spaces of lattice-matched GaSb/InAs0.911Sb0.089 and GaSb/InAs0.932Bi0.068 and strain-balanced InAs/InAsSb, InAs/GaInSb, and InAs/InAsBi superlattices on GaSb. The absorption properties of each of these material systems are directly compared by relating the wavefunction overlap square to the absorption coefficient of each optimized design. Optimal design criteria are provided for key detector wavelengths for each superlattice system. The optimal design mid-wave infrared InAs/InAsSb superlattice is grown using molecular beam epitaxy, and its optical properties are evaluated using spectroscopic ellipsometry and photoluminescence spectroscopy.

Weakly strained highly mismatched BxIn1-xBVyAs1-y (BV = Sb, Bi) alloys

“…2 InBi x As 1-x alloys were grown as InAs-rich alloys by molecular beam epitaxy. 3,4 A non-uniform composition in such films was detected in spite of the small Bi content. 4 This is obviously due to the greater difference in the atomic sizes.…”

“…[1][2][3][4] Alloying Sb or Bi with InAs allows us to obtain rather longer wavelengths corresponding to the mid-infrared spectral region. All such alloys are highly mismatched and, as a result, strongly internally strained.…”

Method of electron affinity evaluation for the type-2 InAs/InAs1−xSbx superlattice

“…All samples were checked for compliance with the ''strain-balanced'' condition [14,15]. This means that the strain occurring between the components of the SL (InAs and InAs 1-x Sb x ) and the buffer layers (GaSb) was small, not causing a large number of dislocations.…”

“…The next approach suggested that the ''strain-balanced'' structure could be reached by assuming equal thickness for the tensile and compressive layers. It could be assumed that the structure is balanced if the following condition is met [15][16][17][18][19]:…”

Modelling of bismuth segregation in InAsBi/InAs superlattices: Determination of the exchange energies

“…Moreover, this compound comprises semiconductor and semimetal components and, because of that, it is expected to possess a temperature-insensitive band gap [10,11]. All these characteristics make InAsBi a promising compound for bandgap engineering, strain compensation and optoelectronic integration [12].…”