Growth and characterization of indium-doped Zn₃P₂ bulk crystals

Abstract

In this paper, we report the crystal growth of indium-doped zinc phosphide bulk crystals to obtain n-type conduction. The crystal growth experiments were carried out by unidirectional solidification from In–Zn–P ternary solution, and n-type Zn3P2 bulk crystals were successfully obtained. It was also revealed that the electrical properties of indium-doped Zn3P2 crystals could be controlled by heat treatment under controlled partial pressure of phosphorus or zinc. The relationship between the electron concentration and the partial pressure of zinc or phosphorus even in indium-doped Zn3P2 can be understood on the basis of defect equilibria, as in the case of undoped Zn3P2. However, the controllable range of the electron concentration was 1010–1013 cm−3, which was too low in terms of the concentration of doped indium. This is due to the low formation energy of the intrinsic acceptor, interstitial phosphorus, and carrier compensation should be discussed. According to recent reports on ab initio calculation, a weakly n-type Zn3P2 is expected to be formed under extremely Zn-rich growth conditions. The results obtained in this study coincide with the prediction based on calculations, and provide useful knowledge for the formation of the p–n junction of Zn3P2.

Multiple morphologies and functionality of nanowires made from earth-abundant zinc phosphide

“…Extrinsic doping, particularly n-type, is not yet fully unravelled. [13][14][15] To overcome these challenges, the nanowire morphology shows promising perspectives. First, their small diameter allows for high-quality epitaxial growth on lattice mismatched substrates through radial stress relaxation.…”

“…30 In principle, the precise flux control in MBE should also enable the controlled incorporation of extrinsic dopants such as Ag, Mg and In. 13,14,[33][34][35] Previously, in addition to thin films and bulk crystals, Zn 3 P 2 has been obtained in the form of randomly oriented nanowires, nanoribbons, and nanotrumpets. [36][37][38][39][40][41][42][43] In most of these studies, nanowires were produced through chemical vapour deposition (CVD) or by a thermochemical method relying on a quartz capsule containing the precursors being heated in a furnace.…”

Heterotwin Zn3P2superlattice nanowires: the role of indium insertion in the superlattice formation mechanism and their optical properties

“…58 We observe to main peaks centred around 869 and 950 nm (1.43 eV and 1.30 eV, respectively), which correspond to sub-bandgap emission, potentially caused by the incorporation of indium in the bulk. 59 First principle simulations should be performed to confirm this hypothesis. We also distinguish a third weaker peak centred around 748 nm (1.66 eV).…”

Reactive Epitaxial Formation of a Mg–P–Zn Ternary Semiconductor in Mg/Zn3P2 Solar Cells

“…Zinc phosphide (Zn 3 P 2 ) is an earth-abundant compound semiconductor with physical properties suitable for TFPVs, such as a direct bandgap of 1.50 eV, an optical absorption coefficient larger than 10 4 cm –1 in the visible range, and a minority-carrier diffusion length of around 5 μm . Zn 3 P 2 typically shows a p-type conductivity due to the intrinsic acceptors, such as interstitial phosphorus and zinc vacancy. , The low formation energies of these point defects cause the difficulty in efficient n-type doping . Therefore, Zn 3 P 2 -based solar cells were fabricated using Schottky junctions or hetero p–n junctions.…”

“…17,18 The low formation energies of these point defects cause the difficulty in efficient n-type doping. 19 Therefore, Zn 3 P 2 -based solar cells were fabricated using Schottky junctions or hetero p−n junctions. The highest conversion efficiency of 6.08% in Zn 3 P 2 -based solar cells was reported by Catalano et al "Schottky" junction with metallic Mg. 20 Interestingly, as is not the case for other promising absorbers, the heterojunctions with the binary chalcogenides resulted in lower conversion efficiency than 6.08%.…”