GaAs-MISFETs With Insulating Gate Films Formed by Direct Oxidation and by Oxinitridation of Recessed GaAs Surfaces

n‐Channel p‐channel enhancement/inversion mode GaAs‐MISFETs with gate insulating layers formed by dry oxi‐nitridation

“…Saturation of the drain current versus the gate voltage change is assumed to occur because the gate voltage lowers the bottom of the conduction band of the insulating film with respect to the conduction band of the n + source. Thus, as suggested by Takebe and colleagues [6], we can see from Fig. 8(c) that the barrier height of GaON is not very high (~0.7 eV).…”

“…Near the flat band voltage of V g = 1 V, the transconductance is degraded in the region of high drain voltages. Such irregular behavior is confirmed in the n-channel depressiontype MOSFET with an insulating film formed only by oxidation [6,11]. Also, the shift of the pinch-off voltage in the positive direction by nitriding is caused by disappearance of the excess positive charge near the oxidation-only interface when nitriding is applied.…”

“…It is believed that further improvement of the characteristics is possible by finding an optimum nitriding time for oxidation of 9 hours. [5] and Takebe and colleagues [6]. From this agreement between the threshold voltage and the flat band voltage, it is considered that an excellent interface without excess charges nearby or in the oxy-nitride insulating film can be obtained in the tested enhancement/inversion-type MISFET.…”

“…As a result, a high-quality insulating film/GaAs interface is obtained. For improvement of the crystal properties of GaAs near the interface, the annealing effect of nitrogen plasma [6] and the variation of the coupling state at the interface [7] can be considered. The detailed mechanisms of these approaches are not clear.…”

“…By using this technique, a depression-type GaAs-MISFET was test-fabricated. A maximum transconductance of 110 mS/mm with a flat band state at V g = 1.1 V was realized [6]. In comparison with depression-type devices, the carriers are closer to the interface in the enhancement/inversiontype devices, so that the influence of the interface is stronger.…”