Indium arsenide antimonide, also known as indium antimonide arsenide or InAsSb ( In As_1-x Sb_x), is a ternary III-V semiconductor compound. It can be considered as an alloy between

indium arsenide Indium arsenide, InAs, or indium monoarsenide, is a narrow-bandgap semiconductor composed of indium and arsenic. It has the appearance of grey cubic crystals with a melting point of 942 °C. Indium arsenide is similar in properties to gallium ars ...

(InAs) and

indium antimonide Indium antimonide (InSb) is a crystalline compound made from the elements indium (In) and antimony (Sb). It is a narrow- gap semiconductor material from the III- V group used in infrared detectors, including thermal imaging cameras, FLIR sy ...

(InSb). The alloy can contain any ratio between arsenic and antimony. InAsSb refers generally to any composition of the alloy.

Preparation

InAsSb films have been grown by

molecular beam epitaxy Molecular-beam epitaxy (MBE) is an epitaxy method for thin-film deposition of single crystals. MBE is widely used in the manufacture of semiconductor devices, including transistors. MBE is used to make diodes and MOSFETs (MOS field-effect transis ...

(MBE), metalorganic vapor phase epitaxy (MOVPE) and liquid phase epitaxy (LPE) on

gallium arsenide Gallium arsenide (GaAs) is a III-V direct band gap semiconductor with a Zincblende (crystal structure), zinc blende crystal structure. Gallium arsenide is used in the manufacture of devices such as microwave frequency integrated circuits, monoli ...

and gallium antimonide substrates. It is often incorporated into layered heterostructures with other III-V compounds.

Thermodynamic stability

Between 524 °C and 942 °C (the melting points of pure InSb and InAs, respectively), InAsSb can exist at a two-phase liquid-solid equilibrium, depending on temperature and average composition of the alloy. InAsSb possesses an additional

miscibility gap A miscibility gap is a region in a phase diagram for a mixture In chemistry, a mixture is a material made up of two or more different chemical substances which can be separated by physical method. It is an impure substance made up of 2 or more ...

at temperatures below approximately 503 °C. This means that intermediate compositions of the alloy below this temperature are thermodynamically unstable and can spontaneously separate into two phases: one InAs-rich and one InSb-rich. This limits the compositions of InAsSb that can be obtained by near-equilibrium growth techniques, such as LPE, to those outside of the miscibility gap. However, compositions of InAsSb within the miscibility gap can be obtained with non-equilibrium growth techniques, such as MBE and MOVPE. By carefully selecting the growth conditions and maintaining relatively low temperatures during and after growth, it is possible to obtain compositions of InAsSb within the miscibility gap that are kinetically stable.

Electronic properties

The

bandgap In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to the ...

and lattice constant of InAsSb alloys are between those of pure InAs (a = 0.606 nm, E_g = 0.35 eV) and

InSb Indium antimonide (InSb) is a crystalline compound made from the elements indium (In) and antimony (Sb). It is a narrow- gap semiconductor material from the III- V group used in infrared detectors, including thermal imaging cameras, FLIR syst ...

(a = 0.648 nm, E_g = 0.17 eV). Over all compositions, the band gap is

direct Direct may refer to: Mathematics * Directed set, in order theory * Direct limit of (pre), sheaves * Direct sum of modules, a construction in abstract algebra which combines several vector spaces Computing * Direct access (disambiguation), ...

, like in InAs and InSb. The direct bandgap displays strong bowing, reaching a minimum with respect to composition at approximately x = 0.62 at room temperature and lower temperatures. The following empirical relationship has been suggested for the direct bandgap of InAsSb in eV as a function of composition (0 < x < 1) and temperature (in

Kelvin The kelvin (symbol: K) is the base unit for temperature in the International System of Units (SI). The Kelvin scale is an absolute temperature scale that starts at the lowest possible temperature (absolute zero), taken to be 0 K. By de ...

E_(x,T) = 0.417 - (1.28\cdot 10^)T - (2.6\cdot 10^)T^ - x(C + 0.182 + (10^)T^) + x^(C - (5.8\cdot 10^) + (10^)T^)

This equation is plotted in the figures, using a suggested bowing parameter of C = 0.75 eV. Slightly different relations have also been suggested for E_g as a function of composition and temperature, depending on the material quality, strain, and defect density.

Applications

Because of its small direct bandgap, InAsSb has been extensively studied over the last few decades, predominantly for use in mid- to long-wave infrared

photodetector Photodetectors, also called photosensors, are devices that detect light or other forms of electromagnetic radiation and convert it into an electrical signal. They are essential in a wide range of applications, from digital imaging and optical ...

s that operate at room temperature and cryogenic temperatures. InAsSb is used as the active material in some commercially available infrared photodetectors. Depending on the

heterostructure A heterojunction is an interface between two layers or regions of dissimilar semiconductors. These semiconducting materials have unequal band gaps as opposed to a homojunction. It is often advantageous to engineer the electronic energy bands in m ...

and detector configuration that is used, InAsSb-based detectors can operate at wavelengths ranging from approximately 2 μm to 11 μm.

References

External links