RECTIFICATION IN HEAVILY DOPED P-TYPE GAAS/ALAS HETEROJUNCTIONS

Experimental and theoretical studies of heavily doped p-type single GaAs/AlAs heterojunctions have been performed. Abrupt junctions doped at 10(18) cm-3 exhibited marked rectifying behavior, in agreement with calculations based on thermionic emission theory. At a doping level of 10(19) cm-3, the current-voltage characteristics were more symmetric, as tunneling current dominated. Grading the junction was found to make the characteristics more linear and symmetric. The results explain the high series resistance of vertical-cavity surface-emitting lasers and demonstrate the need for compositional grading in the p-type multilayer mirrors in those devices.