GaAs based monolithic optoelectronic device integration technology

Abstract

A technology for monolithic device integration of lasers and transistors is described. It is based on a GaAs double modulation-doped epitaxial structure creating both n type and p type conduction channels. In the epitaxy, there are total four levels of contacts including a top level p contact, a bottom level n contact, and two intermediate level channel contacts. The device operation is determined by the contact utilization. The laser operation is achieved within a vertical cavity structure. In laser fabrication, ion implantation is used instead of an oxidized AlAs layer to steer the injection current. The main advantage of ion implantation is accuracy in control of the aperture dimension. For a 12μm diameter VCSEL, the threshold is about 1.7mA. Complementary HFETs are obtained using the n and p channels for the n-HFET and p-HFET respectively. The top p layer and the p-channel are used as n-HFET gate contact and collector (back-gate ) contact respectively. The bottom n layer and the n-channel are used as p-HFET gate contact and collector contact respectively. Complementary HFET operation is demonstrated with balanced threshold voltages of about 0.5V and -0.5V for n-HFETs and p-HFETs, respectively. For 1μm gate length n-HFETs, gm~170ms/mm at Vg=1.2V and Vds=4V, which is similar to that of comparable HEMTs. For 1μm gate length p-HFETs, gm~6.5ms/mm at Vg=1.1V and Vds=4V. With better lithography and shorter gate features, higher gm can be expected. These first results indicate that optoelectronic device performance has not been sacrificed by the monolithic integration.