Ion-implantation technology for improved GaAs MESFETs performance

Electrical properties of Si-implanted and co-implanted with Mg or Be in semi-insulating GaAs was studied. The Si-implanted MESFETs with and without buried p-layer (formed by Mg or Be) have been fabricated and characterized by their d.c. and r.f. performance. The experimental results showed that the device with a buried p-layer can effectively suppress the substrate leakage current (thus good pinch-off characteristic) and obtained higher gain linearity than these without a buried p-layer. For 1 μm × 100μm MESFETs device with co-implantation of Si (∼ 8 × 10¹²cm ^-2) and Be (∼ 6 × 10¹¹cm^-2) demonstrated uniform transconductance (g_m) of ∼115mS mm ^-1 with the gate voltage ranging from - 1 to 1V and reduced pinch-off voltage compared to those with co-implantation of Si and Mg (∼ 6 × 10¹¹ cm ^-2). The measured f_T and f _max of a 1μm × 25 μm MESFET with co-implantation of Si and Be are 10 and 39 GHz, respectively. However, FETs with increased Mg dose (from 6 × 10¹¹cm^-2 to 2 × 10¹² cm^-2) in a buried p-layer can obtain higher transconductance and saturation current.