Strain distributions in the InAlN barrier layers of In0.17Al0.83N/GaN heterostructure field-effect transistors

Using measured gate-source capacitance–voltage (C–V) curves and forward current–voltage (I–V) curves for In0.17Al0.83N/GaN heterostructure field-effect transistors (HFETs) of various gate lengths with normal-Ohmic contacts and side-Ohmic contacts, the strain distributions in the InAlN barrier layers are analyzed. It is found that the compressive strain in the InAlN barrier layer is nearly uniformly distributed between source and drain contacts for devices with side-Ohmic contact processing while it is enhanced and monotonously decreased from the middle to the source/drain contact for devices with normal-Ohmic contact processing. This difference in the strain distributions is attributed to the difference in the lateral diffusing of Ohmic contact metal atoms into the InAlN barrier layer during the different Ohmic contact processing.