Bismuth incorporation and lattice contraction in GaSbBi and InSbBi
III–V-Bi compounds have received considerable attention recently due to a number of interesting material properties. For example, adding a small amount of Bi atoms in conventional III–Vs leads to a large bandgap reduction that occurs predominately in the valence band, about 88 meV/%Bi in GaAsBi. The Bi incorporation affects only the valence band structures and has little influence on electrons. Compared with dilute nitrides, the electron mobility of dilute GaAsBi is much less affected and photoluminescence intensity increases with the Bi incorporation. Dilute GaAsBi also introduces a large spin-orbit split and it has been suggested to use this property to suppress Auger recombination for 1.55 µm lasers on GaAs [1]. So far most experimental studies have been focused on growth of GaAsBi [2], but very little on GaSbBi and InSbBi. Here we report growth of dilute GaSbBi and InSbBi using molecular beam epitaxy (MBE). We have optimized growth conditions aiming at achieving maximum Bi incorporation. Surprisingly X-ray diffraction (XRD) revealed lattice contraction in GaSbBi and InSbBi although Bi atoms have a large atomic radius.
Characterization of Bismuth Containing Compounds
New semiconductor materials with more beneficial properties are continuously demanding for device applications. The heaviest group V and least studied bismuth containing 
compounds have potential applications in electronics, optoelectronics, thermoelectric field and also in fundamental physics. Dilute bismides offer large bandgap bowing in valence band by shifting up the valence band edge. This property offers a grand freedom to engineer band 
structure of semiconductors for potential high-speed electronic and infrared optoelectronic applications. Also it provides a large spin orbit coupling effect which is useful to suppress inter-valence band Auger recombination processes in 1.55 μm lasers. The potential applications for dilute bismides alloys are expected in heterostructure bipolar transistors, light emitting devices, laser diodes and solar cells. Another Bi-containing material Bi2Te3 has 
great thermoelectric property; this property can be used for the applications of cooling different types of devices and for power generation from waste heat. 
 
In this research project, different features have been found and studied for different Bi containing compounds. The samples were grown by a Riber Compact21 MBE system with 
varying growth temperatures and Bi flux. MBE grown Bismuth containing compounds GaSbBi, GaAsBi, InGaAsBi QW, InSbBi and also Bi2Te3 are investigated by atomic force microscopy (AFM), X-ray diffraction (XRD) and Photoluminescence (PL) techniques and then surface morphologies, structural and optical properties are explored from these characterizations, respectively. The MBE grown GaSb1-xBix thin films are established for the first time. Strategies have been taken care of to avoid the formation of Bi droplets and enhance Bi incorporation. From XRD and AFM, maximum Bi incorporation with smooth surface has been obtained for growth temperature of 370 oC and then saturation occurs. InGaAsBi QW samples are characterized by PL at room temperature (RTPL) and also at low temperature (LTPL) for different sample positions and temperatures, respectively. When Bi is incorporated, 10 times higher PL intensity has been achieved comparing with the reference InGaAs QW sample. For Bi2Te3 samples grown on Si substrates, growth temperature of 240°C showed the best feature both in AFM and XRD characterizations. 
 
Since this project on Bi-containing compounds is still under experimental demonstration, there is a lot to do for improving the material quality. One important future goal of this project is to establish the relation between the fundamental physical parameters such as lattice constant, bandgap and effective mass etc and the Bi composition. Getting hold of improved quality Bi containing QWs at 1.55 μm is another goal of this research in future. The future Bi containing compounds research is expected to be accelerated at a much fast pace.
Energy-gap variation of the (thallium selenide)x-(indium selenide)1 − x mixed crystals (x = 0.1, 0.2, …, 0.9, 1.0)
Abstract Crystals of the Tl 2x In 2(1 − x) Se 2 family (for x = 0.1, 0. 2 , …, 0.9, 1.0) were grown and their energy gap was studied in the intrinsic region of the corresponding lnσ-1000/T characteristics. The energy gap, the intrinsic conductivity and the band discontinuity were found to depend on the Tl-content x, obeying Kurnakov's rule.