Growth of Nitride Heteroepitaxial Transistor Structures: from Epitaxy of Buffer Layers to Surface Passivation

Abstract

It is demonstrated that it is possible to use the ammonia molecular beam epitaxy for growing structurally perfect high-ohmic GaN layers which allow generating SiN/Al(Ga)N/GaN heterostructures for transistors with a high mobility of electrons. The growth conditions are determined for GaN layers with smooth surface morphology (with a mean-squared deviation of $${\sim}$$ 2 nm) appropriate for creating sharp heteroboundaries. The possibility of improving the crystalline perfection of GaN layer due to the use of buffer high-temperature AlN layer (with the growth temperature above 940 $${}^{\circ}$$ C) is demonstrated. It was shown that in situ surface passivation of Al(Ga)N/GaN heterostructures by the ultrathin SiN layer allows generating normally closed transistors with unprecedented low values of the current collapse ( $${\sim}1\%$$ ).