Negative differential resistance in GaN homojunction tunnel diodes and low voltage loss tunnel contacts

The current-voltage characteristics and metastability in GaN pthornthorn/nthornthornhomojunction tunnel diodes and nthornthorn/pthornthorn/i/n tunnel-contacted diodes grown via metal modulated epitaxy have been investigated. The room temperature negative differential resistance (NDR) beginning at similar to 1.35V is reported for GaN homojunction devices grown on sapphire. The NDR vanishes, and the conductivity increases as multiple I-V sweeps are performed, thus suggesting that charge trapping states with long trap lifetimes exist at defect sites, and these traps play a crucial role in the tunneling mechanism. Additionally, the use of extremely high n-type (N-D similar to 4.6 x 10(20) cm(-3)) and p-type (N-A similar to 7.7 x 10(20) cm(-3)) doping results in a near linear characteristic with minimal rectification at current densities less than 200 A/cm(2) and soft rectification above this current density. Forward-bias tunneling and NDR are still present at 77 K. The highest silicon-doped nthornthorn/pthornthorn/i/n tunnel-contacted pin diode demonstrates a turn-on voltage of 3.12 V, only 0.14V higher than that of the pin control diode, and an improved specific on-resistance of 3.24 x 10(-4) X cm(2), which is 13% lower than that of the control pin diode. Published by AIP Publishing.