A low-gate-leakage-current GaAs MESFET with a thin epitaxial silicon layer

An n-channel depletion-mode GaAs MESFET with an Al gate and a 6-A epitaxial Si layer between the metal and the GaAs, grown in situ by molecular beam epitaxy, is described. Its DC electrical characteristics are compared with a similar control structure grown without the Si layer. The gate leakage current in the Al/Si/GaAs MESFETs was three to four orders of magnitude lower than in the control structure, due to all increased barrier height in the Al/Si/n-GaAs Schottky gate of 1.04 eV, versus 0.78 eV for the Al/n-GaAs structure. The differences in threshold voltages, I-V characteristics, and transconductances between the two devices are consistent with an enhanced effective barrier height for the Al/Si/GaAs MESFET.< >