Serge Karboyan

Impact of buffer leakage on intrinsic reliability of 650V AlGaN/GaN HEMTs

The role of buffer traps (identified as CN acceptors through current DLTS) in the off-state leakage and dynamic Ron of 650V rated GaN-on-Si power devices is investigated. The dynamic Ron is strongly voltage-dependent, due to the interplay between the dynamic properties of the CN traps and the presence of space-charge limited current components. This results in a complete suppression of dyn Ron degradation under HTRB conditions between 420V and 850V.

Interface State Artefact in Long Gate-Length AlGaN/GaN HEMTs

Dispersion in capacitance and conductance measurements in AlGaN/GaN high-electron mobility transistors is typically interpreted as resulting from interface states. Measurements on varying gate-length devices and a model of an interface-trap-free device are used to demonstrate that the distributed-resistance-induced dispersion is significant for 1-MHz measurements if the gate length exceeds ~10 μm. Hence, interface state density measurements using the conductance technique need to use shorter gate-length devices in order to avoid this artefact.

Impact of Silicon Nitride Stoichiometry on the Effectiveness of AlGaN/GaN HEMT Field Plates

Field plate (FP) control of current collapse and channel electric field distribution in AlGaN/GaN High Electron Mobility Transistors is investigated as a function of low-pressure chemical vapor deposition silicon-nitride stoichiometry. Dependence of current collapse is seen, however, this also leads to enhanced FP pinchoff voltages and higher leakage. Electric field concentration at the gate edge is indicated by measuring OFF-state Two dimensional electron gas position with a sense contact technique. A model explaining the FP threshold variation due to barrier leakage is proposed.

Negative dynamic Ron in AlGaN/GaN power devices

Through optimization of the GaN buffer structure, 650V rated AlGaN/GaN power devices with negative dynamic Ron are obtained. By judicious tuning of the resistivity of the [C]-doped and unintentionally-doped (UID) layers (i.e. the charge transport properties in these layers), positive rather than the deleterious negative charged trapping can be achieved. Long term reliability testing shows that the positive charge can be retained for days.

Impact of buffer charge on the reliability of carbon doped AlGaN/GaN-on-Si HEMTs

Charge trapping and transport in the carbon doped GaN buffer of an AlGaN/GaN-on-Si high electron mobility transistor (HEMT) have been investigated. Back-gating and dynamic Ron experiments show that a high vertical leakage current results in significant long-term negative charge trapping in the buffer leading to current collapse under standard device operating conditions. Controlling current-collapse requires control of not only the layer structures and its doping, but also the precise balance of leakage in each layer.

On the origin of dynamic R on in commercial GaN-on-Si HEMTs

Abstract There are huge differences in dynamic on-resistance Ron, also known as current-collapse, between current GaN power HEMT technologies. Here we illustrate this fact with dynamic Ron measurements on two commercially available devices from 2 different manufacturers, with one showing more than a factor of 2 increase in dynamic Ron after OFF-state drain bias (type 1) and the other one