Zinc cadmium phosphide arsenide

Zinc cadmium phosphide arsenide (Zn-Cd-P-As) is a quaternary system of group II (IUPAC group 12) and group V (IUPAC group 15) elements. Many of the inorganic compounds in the system are II-V semiconductor materials. The quaternary system of II₃V₂ compounds, (Zn_1−xCd_x)₃(P_1−yAs_y)₂, has been shown to allow solid solution continuously over the whole compositional range.^[1] This material system and its subsets have applications in electronics, optoelectronics, including photovoltaics, and thermoelectrics.^[2]

List of all binary compounds

This system of elements contains numerous binary compounds and their solid solutions.

Stable at atmospheric pressure

The binary compounds thermodynamically stable at atmospheric pressure are listed in the following table:^[1][3]

Anion  Cation	P		As
Zn	Zn3P2 ZnP2	α″ (or α) and β[4] α and β[4]	Zn3As2 ZnAs2	α, α′ and β[5] one polymorph[5]
Cd	Cd3P2 CdP2 Cd2P3 CdP4 Cd6P7	one polymorph[6] – [7] – unconfirmed[7]	Cd3As2 CdAs2	α, α′, α″ and β[3] α and δ[3]

Metastable or unstable at atmospheric pressure

Compounds metastable or unstable at atmospheric pressure are the following:

Anion  Cation	P		As
Zn	ZnP2 ZnP4 Zn7P10 Zn3P2	high-pressure rhombohedral phase high-pressure tetragonal phase high-pressure orthorhombic phase high-pressure phase	Zn3As2 ZnAs	high-pressure phase high-pressure phase, low and high-temperature polymorphs
Cd	Cd3P2	high-pressure phase	Cd3As2 CdAs CdAs4	high-pressure phase high-pressure phase, low and high-temperature polymorphs [3]

Quaternary compounds

The compounds of the form II₃V₂ have similar crystalline structures and exhibit full solid solution over the whole compositional range. The compounds of the form II-V₂ allow only partial solid solution.^[3]

Ternary compounds

The binary compounds in this system form a wide range of solid solutions. This miscibility reflects the close similarity of the structures of the binary phases. The IIV₂ compounds exhibit wide solid solution ranges with CdP₄ even though the stoichiometry and structures of the components differ.^[3]

The optoelectronic and band properties of some ternary compounds have also been studied. For example, the bandgap of Zn₃(P_1−yAs_y)₂ solid solutions is direct and tunable from 1.0 eV to 1.5 eV. This solubility enables the fabrication of tunable nanowire photodetectors.^[8] The solid solution (Zn_1−xCd_x)₃As₂ exhibit a topological phase transition at x ~ 0.62.^[9]

Notable binary compounds

Cadmium arsenide (Cd₃As₂)

Main article: Cadmium arsenide

Cadmium arsenide is a 3D Dirac semimetal exhibiting the Nernst effect.

Zinc phosphide (Zn₃P₂)

Main article: Zinc phosphide

Zinc phosphide is a semiconductor material with a direct band gap of 1.5 eV^[10] used in photovoltaics.^[11] It is also used as a rodenticide in the pest control industry.

Zinc arsenide (Zn₃As₂)

Main article: Zinc arsenide

Zinc arsenide is a semiconductor material with a band gap of 1.0 eV.^[12]