Shallow donors in magnetic fields in zinc-blende semiconductors. II. Magneto-optical study of InSb under hydrostatic pressure

Four intraimpurity transitions between the shallow states of residual donors were studied as a function of a high magnetic field up to 19 T and of a hydrostatic pressure up to 1.1 GPa in nominally undoped n-type InSb samples. The measurements were performed mainly with the photoconductivity technique in the 5--30-cm^-1 spectral region using a far-infrared-laser system. Good quantitative agreement with the multiband approach proposed by Trzeciakowski et al. (preceding paper) is obtained at zero pressure as well as under pressure (provided that the pressure variation of the dielectric constant is taken into account) in a wide range of high effective magnetic fields 10<{γ}<130 [{γ}={}ωc/(2 Ry*)]. The study of the chemical shifts for the observed donors allows for the determination of the matrix elements of the localized parts of the impurity potentials (S{}V_locS). For the deepest of the donors (donor A) this matrix element increases significantly with pressure. Moreover, at pressures around 0.65 GPa, the ground state of the donor A anticrosses with another level of the same impurity center, resonant with the conduction band in the absence of field and pressure. Detailed study of the anticrossing within a simple two-level model shows that the ``resonant'' level can be treated as deep, i.e., essentially bound by Vloc, while the Coulomb potential shifts its position by about 0.1 eV.