Gallium arsenide antimonide, also known as gallium antimonide arsenide or GaAsSb ( Ga As_(1-''x'') Sb_''x''), is a ternary III-V semiconductor compound; ''x'' indicates the fractions of arsenic and antimony in the alloy. GaAsSb refers generally to any composition of the alloy. It is an alloy of

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 ...

(GaAs) and

gallium antimonide Gallium antimonide (GaSb) is a semiconducting compound of gallium and antimony of the III-V family. It has a room temperature lattice constant of about 0.610 nm. It has a room temperature direct bandgap of approximately 0.73 eV. History The int ...

(GaSb).

Preparation

GaAsSb 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

and

indium phosphide Indium phosphide (InP) is a binary semiconductor composed of indium and phosphorus. It has a face-centered cubic ("zincblende (crystal structure), zincblende") crystal structure, identical to that of gallium arsenide, GaAs and most of the List of ...

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

Thermodynamic Stability

GaAsSb has a

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 751 °C. This means that intermediate compositions of the alloy below this temperature are thermodynamically unstable and can spontaneously separate into two phases: one GaAs-rich and one GaSb-rich. This limits the compositions of GaAsSb that can be obtained by near-equilibrium growth techniques, such as LPE, to those outside of the miscibility gap. However, compositions of GaAsSb within the miscibility gap can be obtained with non-equilibrium growth techniques, such as MBE and MOVPE. By carefully selecting the growth conditions (e.g., the ratios of precursor gases in MOVPE) and maintaining relatively low temperatures during and after growth, it is possible to obtain compositions of GaAsSb within the miscibility gap that are kinetically stable. For example, this makes it possible to grow GaAsSb with the composition GaAs_0.51Sb_0.49, which, while normally within the miscibility gap at typical growth temperatures, can exist as a kinetically stable alloy. This composition of GaAsSb is latticed matched to InP and is sometimes used in heterostructures grown on that substrate.

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 GaAsSb alloys are between those of pure GaAs (a = 0.565 nm, E_g = 1.42 eV) and GaSb (a = 0.610 nm, E_g = 0.73 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 GaAs and GaSb. Furthermore, the bandgap displays a minimum in composition at approximately x = 0.8 at T = 300 K, reaching a minimum value of E_g = 0.67 eV, which is slightly below that of pure GaSb.

Applications

GaAsSb has been extensively studied for use in

heterojunction bipolar transistor A heterojunction bipolar transistor (HBT) is a type of bipolar junction transistor (BJT) that uses different semiconductor materials for the emitter and base regions, creating a heterojunction. The HBT improves on the BJT in that it can handle si ...

s. It has also been lattice-matched with

InGaAs Indium gallium arsenide (InGaAs) (alternatively gallium indium arsenide, GaInAs) is a ternary alloy (chemical compound) of indium arsenide (InAs) and gallium arsenide (GaAs). Indium and gallium are group III elements of the periodic table while ...

on InP to create and study a

two-dimensional electron gas A two-dimensional electron gas (2DEG) is a scientific model in solid-state physics. It is an Fermi gas, electron gas that is free to move in two dimensions, but tightly confined in the third. This tight confinement leads to quantized energy levels ...

. A GaAsSb/GaAs-based heterostructure was used to make a near-infrared

photodiode A photodiode is a semiconductor diode sensitive to photon radiation, such as visible light, infrared or ultraviolet radiation, X-rays and gamma rays. It produces an electrical current when it absorbs photons. This can be used for detection and me ...

with peak responsivity centered at 1.3 μm. GaAsSb can be incorporated into III-V–based

multi-junction solar cell Multi-junction (MJ) solar cells are solar cells with multiple p–n junctions made of different semiconductor materials. Each material's p–n junction will produce electric current in response to different wavelengths of light. The use of mult ...

s to reduce the tunneling distance and increase the tunneling current between adjacent cells..

References

External links

Properties of GaAsSb
{{Antimony compounds Antimonides Arsenides Gallium compounds III-V compounds