The PI will investigate a new, proprietary structure in the GaAs/A1GaAs material system which will allow laser diodes to be fabricated in HEMT (High Electron Mobility Transistor) material. This will allow easy integration of HEMT drive electronics with low capacitance, high speed laser diodes for future OEIC (Optoelectronic Integrated Circuit) applications. The process is based on the MBE growth technique of Plane Selective Doping which causes Si to incorporate as both p- and n-type dopant along different growth planes. This allows an abrupt lateral change from p- to n-type HEMT 2-d carrier layers, thus forming a pn junction. Very preliminary "proof of principle" work has yielded good pn junctions with spontaneous light emission at the GaAs bandgap wavelength but no lasing yet. The mask set proposed will contain single HEMT devices of both p- and n-type carriers, single laser structures of various active lengths for proper characterization, ohmic contact test structures to determine the contact resistance to the 2-d gases, and integrated laser/HEMT driver circuits. Ion-implanted contacts will be tried to reduce contact resistance, and TEM studies will be done of the pn junction to determine how abrupt it is.
