Abstract
The performance of GaN-on-Silicon electronic devices is severely degraded by the presence of a parasitic conduction pathway at the nitride-substrate interface which contributes to switching losses and lower breakdown voltages. The physical nature of such a parasitic channel and its properties are however, not well understood. We report on a pronounced thickness dependence of the parasitic channel formation at AlN/Si interfaces due to increased surface acceptor densities at the interface in silicon. The origin of these surface acceptors is analyzed using secondary ion mass spectroscopy measurements and traced to thermal acceptor formation due to Si-O-N complexes. Low-temperature (5 K) magneto-resistance (MR) data reveals a transition from positive to negative MR with increasing AlN film thickness indicating the presence of an inversion layer of electrons which also contributes to parasitic channel formation but whose contribution is secondary at room temperatures.
Highlights
The physical origin of the parasitic substrate channel can be traced back to the growth of III-nitride stacks on silicon
AlN films are strained in tension during growth on Si and any piezoelectric polarization field is expected to add to the existing spontaneous polarization component[12,21,25]
Using a combination of C-V and conductance spectroscopy we show that the parasitic channel formed at the AlN/Si interface is due to increased acceptor density at the surface of the substrate and it demonstrates a rather striking dependence on the thickness of the AlN films grown
Summary
The performance of GaN-on-Silicon electronic devices is severely degraded by the presence of a parasitic conduction pathway at the nitride-substrate interface which contributes to switching losses and lower breakdown voltages. In view of the potential held out by GaN-on-Si electronics, a thorough understanding and control of all aspects affecting their device performance is timely and of utmost importance One such issue is the presence of a parasitic channel at the epitaxial nitride-silicon interface. The presence of a parasitic conduction pathway at the nitride-silicon interface is detrimental in terms of the switching efficiency and reduces the output power that can be extracted from these devices[7,11,12]. Substrate parasitic channel formation is a pressing technological issue affecting the performance and reliable operation of GaN-on-Si transistors for both RF and power device applications. We first examine the possible sources of the parasitic substrate channel and follow it up with our experimental results, discussions and conclusions
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