Doping dependence of semiconductor–metal transition in InP at high pressures

Abstract

The resistivity of selenium-doped n-InP single crystal layers grown by liquid-phase epitaxy with electron concentrations varying from 6.7×10 18 to 1.8×10 20 cm -3 has been measured as a function of hydrostatic pressure up to 10 GPa. Semiconductor-metal transitions were observed in each case with a change in resistivity by two to three orders of magnitude. The transition pressure p c decreased monotonically from 7.24 to 5.90 GPa with increasing doping concentration n according to the relation p c = p o [1 - k ( n / n m ) α ], where n m is the concentration (per cubic centimetre) of phosphorus donor sites in InP atoms, p o is the transition pressure at low doping concentrations, k is a constant and α is an exponent found experimentally to be 0.637. The decrease in p c is considered to be due to increasing internal stress developed at high concentrations of ionized donors. The high-pressure metallic phase had a resistivity (2.02–6.47)×10 -7 Ω cm, with a positive temperature coefficient dependent on doping.