Normally-OFF Diamond Reverse Blocking MESFET

Schottky contacts have been used to fabricate normally- OFF lateral reverse-blocking MESFETs on p-type (boron-doped) O-terminated monocrystalline diamond. The devices utilized an ohmic source contact but both gate and drain contacts were Schottky in nature. Boron-doped p-channel diamond MESFETs reported to date display the less attractive normally- ON characteristics. Here, the normally- OFF transistor delivered a current level of ~1.5 $\mu $ Amm ⁻¹ at a negative ${V}_{\text {GS}}$ of 0.8 V and a transconductance ( ${g}_{m}$ ) of $16~\mu $ Smm ⁻¹ , measured at room temperature (RT); at a temperature of 425 K, these values rose to $\sim 70~\mu $ Amm ⁻¹ for ${I}_{\text {DS}}$ and a ${g}_{m}$ value of $260~\mu $ Smm ⁻¹ . In both cases, a negligible gate leakage current was measured with no breakdown apparent at the maximum field investigated here ( $3.7\times 10^{{5}}$ V/m ⁻¹ ). The Schottky gate demonstrates a well-behaved control of the channel even at higher temperatures. The high-temperature operation, normally- OFF behavior, and diamond’s inherent radiation hardness make this transistor promising for harsh environment applications.