Strained InAs quantum wells confined by AlxGa0.48-xIn52As barriers on InP substrate (3.2 % mismatch) were fabricated by a new growth technique which prevents islanding of the highly strained InAs layers. Under In-rich conditions (virtual surfactant MBE) strain relaxation is suppressed for kinetic reasons, and InAs/AlxGa0.48-xIn52As interfaces of high structural perfection were obtained even far beyond the critical InAs layer thickness. Spontaneous emission from InAs single quantum wells up to 2.4 mu m at 300 K and stimulated emission from electrically pumped laser structures has been achieved.