High Off-state Breakdown Research Articles

Schottky-barrier normally off GaN/InAlN/AlN/GaN HEMT with selectively etched access region

A Schottky-barrier normally off InAlN-based high-electron-mobility transistor (HEMT) with selectively etched access regions, high off-state breakdown, and low gate leakage is presented. Metal-organic chemical vapor deposition-grown 1-nm InAlN/1-nm AlN barrier stack is capped with a 2-nm-thick undoped GaN creating a negative polarization charge at a GaN/InAlN heterojunction. Consequently, the gate effective barrier height is increased, and the gate leakage as well as the equilibrium carrier concentration in the channel is decreased. After removal of the GaN cap at access regions by using a highly selective dry process, the extrinsic channel becomes populated by carriers. Normally off HEMTs with 8-μm source-to-drain distance and 1.8-μm -long symmetrically placed gate showed a source drain current of about 140 mA/mm. The HEMT gate leakage at a drain voltage of 200 V and grounded gate is below 10-7 A/mm with a three-terminal device breakdown of 255 V. The passivated InAlN surface potential has been calculated to be 1.45 V; significant drain current increase is predicted for even lower potential.

Improved breakdown voltage of AlGaN/GaN HEMTs grown on Si substrates using partially Mg-doped GaN buffer layer by MOCVD

AlGaN/GaN high electron mobility transistors (HEMTs) were grown on Si substrates by MOCVD. In the HEMT structure, a 1 μm GaN buffer layer was partially doped with Mg in an attempt to increase the resistivity and minimize the buffer leakage. The AlGaN/GaN HEMTs grown on undoped and partially Mg-doped GaN buffer layers were processed and the DC characteristics of the devices were characterized for comparing the effect of Mg doping. For the device with the partially Mg-doped GaN buffer layer, a lower drain leakage current density of 55.8 nA/mm, a lower gate leakage current density of 2.73 μA/mm, and a higher off-state breakdown voltage of 104 V were achieved with device dimensions Lg/Wg/Lgs/Lgd=1/10/1/1 μm, better than the device with the undoped GaN buffer layer, which has a higher drain leakage current density of 9.2 μA/mm, a higher gate leakage current density of 91.8 μA/mm, and a lower off-state breakdown voltage of 87 V with the same device dimensions.

On the InGaP/GaAs/InGaAs camel-like FET for high-breakdown, low-leakage, and high-temperature operations

A new field-effect transistor using a high-barrier n/sup +/ -GaAs/p/sup +/-InGaP/n-GaAs camel-like gate and GaAs/InGaAs heterostructure-channel has been fabricated successfully and demonstrated. Experimentally, an ultra high gate-drain breakdown voltage of 52 V, a high drain-source operation voltage over 20 V with low leakage currents, and a high drain-source off-state breakdown voltage of 39.7 V are obtained for a 1/spl times/100 /spl mu/m/sup 2/ device. The high breakdown behavior is attributed to the use of high barrier camel-like gate and heterostructure channels to reduce the undesired leakage current. Furthermore, the studied device also shows high breakdown behavior in a high temperature environment and good microwave characteristics. Therefore, based on these characteristics, the studied device is suitable for high-breakdown, low-leakage, and high-temperature applications.