GaAs-InGaAs doped-channel negative-differential-resistance field-effect transistor (NDRFET)

In this paper we fabricate a GaAs/n⁺InGaAs/GaAs doped-channel FET device with significant transistor performance. The use of the doped-channel structure also has the benefits of: (1) enhanced electron mobility and velocity in the InGaAs channel; and (2) elimination of the undesired DX centers or persistent photoconductivity effect. Study of the structure reveals that it exhibits the anomalous negative differential resistance (NDR) phenomenon. We conclude that the NDR performance is related to the existence of deep-level electron traps and the real-space transfer effect. Because only part of the fabricated devices exhibit NDR phenomena, the nonuniformly distributed deep-level electron traps related to the substrate or MOCVD growth process may be expected. The existence of electron traps enhances the decrease of channel current resulting from the real-space transfer effect. When the channel electrons gain enough energy from the accelerating field (at higher V_DS regime), they may inject into the neighboring GaAs layers and become trapped in the deep levels. This causes the reduction of conduction current and occurrence of NDR behavior