This contribution drafts the problems of the AlGaInP material system and its consequences for the laser applications in vertical-cavity surface-emitting lasers (VCSEL). The epitaxial and technological solutions to overcome at least parts of the inherent problems were discussed. Calculated data by a cylindrical heat dissipation model were compared with measured power-current curves of 660nm oxide-confined VCSEL to improve the heat removal out of the device. At high temperatures pulsed operation of a 670nm VCSEL is demonstrated, where we could exceeded 0.5mW at +120°C and at +160°C still 25µW optical output power were achieved.