Quantum well on the $n$-GaAs surface irradiated by argon ions

The density of states of the valence band of a $p$-GaAs layer formed on an $n$-GaAs surface owing to the bombardment by $2500$-eV Ar$^+$ ions has been studied by photoelectron spectroscopy. A number of peaks have been detected in the spectrum of the edge of the valence band in the binding energy range $E_{\mathrm{V}}< 1.2$ eV. Their number and energy positions correspond to the quantum confinement levels calculated for a hole quantum well on the surface with the width about the ion penetration depth $R_{\mathrm{p}}=3.6$ nm. Electronic transitions from these levels to the bottom of the conduction band have been revealed in the spectrum of characteristic energy losses of electrons reflected from the surface. Thus, it has been shown that the action of the argon ion beam on $n$-GaAs results in the formation of a quantum well on the surface.