Comparison of high mobility AlGaN/GaN heterostructures grown by MBE on HVPE GaN templates and directly nucleated on sapphire

We compare molecular beam epitaxy growth of high electron mobility AlGaN/GaN heterostructures grown homoepitaxially on semi-insulating (SI) GaN templates prepared by hydride vapor phase epitaxy (HVPE) with structures grown completely by MBE on sapphire substrates. The quality of our MBE grown AlGaN/GaN heterostructures on HVPE templates has been proven by a record low temperature two-dimensional electron gas (2DEG) mobility of 75,000 cm/sup 2//Vs at T=4.2 K. Recently, we have developed Zn-compensated HVPE GaN templates that are highly resistive at room temperature (/spl rho//spl sim/10/sup 8//spl Omega/cm). MBE grown heterostructures grown on SI HVPE GaN are electrically isolated from the substrate at all temperatures from 300 K down to T=4.2 K. We report on the first high electron mobility transistors (HEMTs) grown by MBE on a HVPE GaN template.