Enhanced effect of polarization on electron transport properties in AlGaN/GaN double-heterostructure field-effect transistors

In order to understand the effect of polarization on the electron transport properties in AlGaN/GaN heterostructures, the dependence of the two-dimens ional electron gas mobility on the density has been examined both in the Ga N single- and 200-Angstrom GaN double- heterostructure field-effect transis tors, by means of the Hall effect measurement under the gate-voltage applic ation at 4.2 K. In the single heterostructure, a maximum mobility of 5700 c m(2)/V s has been obtained at 9.0x10(12) cm(-2); whereas in the double hete rostructure, a higher maximum mobility of 8100 cm(2)/V s has been obtained at a lower electron density of 6.8x10(12) cm(-2). The results have been ana lyzed in terms of potential profiles and electron distributions in both str uctures where both piezoelectric and spontaneous polarization effects are t aken into account. The analysis has shown that the observed mobility enhanc ement is mainly due to the enhanced polarization-induced electron confineme nt in the double heterostructure and, additionally, to the improvement of t he interface roughness in the structure. (C) 2000 American Institute of Phy sics. [S0003-6951(00)01421-2].