MOLECULAR-BEAM EPITAXY OF VERTICALLY COMPACT ALXGA1-XAS GAAS LASER-HEMT STRUCTURES FOR MONOLITHIC INTEGRATION/

Vertically compact AlxGa1-xAs/GaAs laser structures with Al0.3Ga0.7As/ AlAs SPSL-cladding layers were grown on top of HEMT structures by MBE and investigated with regard to series resistance. We found an exponen tial dependence of series resistance R-s with AlAs and Al0.3Ga0.7As SP SL-layer thicknesses at ambient temperature. Laser-HEMT structures for monolithic integration were grown and lasers were processed. For 3 x 200 mu m(2) 3-QW-lasers, suitable for high-frequency performance, thre shold currents of 20 mA and series resistances below 12 Omega were obt ained. The slope of the linear regression of the I-th values as a func tion of mesa width yielded a low threshold current density j(ch) of 48 0 A/cm(2). Reduction of the p-cladding thickness from 600 nm down to 4 50 nm shows no increase in threshold current density if the p-dopants are kept from diffusing into the active region. This clearly demonstra tes that laser structures fur monolithic integration can be designed v ery compact without loosing performance.