A novel four-terminal device grown by molecular beam epitaxy

Abstract

A novel four‐terminal device TBGFET (top‐back‐gate field‐effect transistor) grown by MBE is fabricated. An n+ Sn‐doped GaAs buried contact layer is grown on a Cr‐doped semi‐insulating substrate first, and an undoped Al0.4Ga0.6As insulating layer and Sn‐doped GaAs channel are grown subsequently. Nonselective mesa etch is used as device isolation and selective etch is adopted to open the back‐gate contact window. TBGFET works as a MESFET and MISFET with a common channel but separately controlled by top gate and back gate. We can adjust the transconductance and current level at room temperature as we wish by properly applying negative bias to the back gate or top gate. The top gate threshold voltage Vt=−1.6 V and back gate threshold voltage Vbt=−5.4 or −1.5 V are obtained. Either Vt or Vbt can be changed without influencing the other one. Based on the above properties, a number of applications of TBGFET are proposed.