Effect of strained layer on GaAs power field effect transistor using low temperature buffer

Abstract

The radio frequency (RF) output power and the drain current efficiency of fabricated GaAs field effect transistor (FET) devices at 2.3 GHz have been improved by inserting a strained layer of InGaAs between the GaAs active channel layer and the GaAs low temperature buffer (LTB) layer grown by molecular beam epitaxy (MBE). The current transient spectroscopy, used to determine the drain current of the power FET with a LTB, indicated the degradation by RF power at an activation energy of 0.3 to 0.4 eV. The deep level transient spectroscopy measurement of power FET, using a LTB with strained layer of InGaAs, also indicated the existence of a trap having similar activation energy. This trap was decreased considerably by increasing the InAs mole fraction of InGaAs strained layer from 0.1 to 0.3. As a result RF output power improved slightly; however, there was a significant improvement in the drain current efficiency of the device fabricated on the new epi-structure when compared to device of otherwise identical structure without the strained layer. Through the comparison of the data for epi-structure with and without the LTB layer, it became evident that the aforesaid electron trap with an activation energy of 0.3–0.4 eV originates from the LTB layer.