Direct monitoring of thermally activated leakage current in AlGaInP laser diodes

Using specially prepared structures, we have observed emission from a layer of direct-gap "monitor" material placed between the p-contact layer and p- cladding layer of a conventional 670 nm GaInP laser diode at room temperatu re. This observation provides direct evidence for electron leakage through the p-cladding layer in these devices. Furthermore, although emission from the quantum well and waveguide core both pin above threshold, indicating th at the Fermi levels clamp throughout the active region, the monitor emissio n continues to rise above threshold. This is characteristic of a drift comp onent to the leakage current, which we have confirmed by a simulation of th e carrier transport processes through the cladding layer with and without d rift. (C) 1999 American Institute of Physics. [S0003-6951(99)00417-9].