ABSTRACT
Abstract. In order to clarify the effect of the A1 composition on the twodimensional electron gas (2DEG) transport properties in Si-doped AlGaN/GaN heterostructure field-effect transistors (HFETs), the 2DEG mobility has been examined as the function of the 2DEG density for the A1 composition up to 0.3 below and above room temperature. Above room temperature (up to 400°C), the 2DEG mobility for the same 2DEG density has been shown to increase with increasing the A1 composition as the result of the increased polarization-induced electrons. For a very high 2DEG density of 2x1013 cm'2, the HFET with the A1 composition of 0.3 has exhibited high 2DEG mobilities more than 1000 cm2/Vs at room temperature and about 140 cm2/Vs at 400°C. Thus the HFETs with high A1 compositions are promising from the viewpoint of both the 2DEG mobility and the 2DEG density. 1
AlGaN/GaN heterostructure field-effect transistors (HFETs) have recently emerged as the attractive transistors suitable for high-temperature and high-power microwave applications [1 - 11]. Understanding the two-dimensional electron gas (2DEG) transport properties in HFETs with high A1 compositions is indispensable for further improving device performances, because unrelaxed HFETs with higher A1 compositions leads to increase the 2DEG density [12-14] and leads to improve the Schottky characteristics of the gate, as the result of the enlarged polarization effects and the enlarged conduction-band discontinuity.
