Low p-type contact resistance by field-emission tunneling in highly Mg-doped GaN

Abstract

Mg-doped GaN with a net acceptor concentration (NA-ND) in the high 1019 cm−3 range was grown using ammonia molecular-beam epitaxy. Electrical properties of NiO contact on this heavily doped p-type GaN were investigated. A potential-barrier height of 0.24 eV was extracted from the relationship between NA-ND and the specific contact resistivity (ρc). We found that there is an optimum NA-ND value of 5 × 1019 cm−3 for which ρc is as low as 2 × 10−5 Ω cm2. This low ρc is ascribed to hole tunneling through the potential barrier at the NiO/p+-GaN interface, which is well accounted for by the field-emission model.

Influence of Mg Out‐Diffusion Effect on the Threshold Voltage of GaN‐Based p‐Channel Heterostructure Field‐Effect Transistors

“…Although a small concentration of Mg in the p‐GaN layer is conducive to realizing E‐mode devices, it is detrimental to fabricating ohmic contacts for p‐GaN. [ 28 ] Nevertheless, a large doping concentration will result in a high leakage current of devices. As a result, Mg concentration in the p‐GaN layer should be designed within a reasonable range.…”

Origins of the Schottky Barrier to a 2DHG in a Au/Ni/GaN/AlGaN/GaN Heterostructure

“…This work aims to develop an understanding of the inherently high contact resistance to a 2DHG in GaN. The high resistivity has been attributed partially to a poor efficiency of Mg activation, usually lower than 1%, even at a doping concentration of 1.0E20 cm –3 , due to the high activation energy of ∼170 meV in Mg-doped MOCVD-GaN. , Recent progress via low temperature molecular beam epitaxy (MBE) has demonstrated a reduction of donor-like defects that tend to compensate for the p-type doping, to levels of ∼1.0E17 cm –3 , resulting in higher activation by a factor of 10. Regrown contacts in combination with high work-function metals such as Ni/Pd can help reduce the contact resistivity .…”

“…This behavior is far from ideal thermionic field-emission theory used previously to extract the SBH to p-GaN, ,,, which assumes a single SB fitted to the entire range of temperature, from a plot of resistivity versus temperature, which is clearly not the case when n ≠ 1. Okumura reports three ranges of behavior for their contacts based on (i) N A – N D < 2e19/cm 3 , resulting in the onset of Schottky behavior, (ii) Ohmic behavior between 3E19–7E19/cm 3 attributed to hole tunneling via field emission, whereas (iii) higher doping concentrations show a peculiar increase in resistivity due to deactivation of Mg but without any accompanying Schottky behavior in their I – V . They propose this behavior to arise from tunneling through deep level defects and interfacial traps of compounds including accumulated Mg at the surface, via trap assisted tunneling, consistent with the high nonideality factors we observe.…”

“…Okumura reports three ranges of behavior for their contacts based on (i) N A −N D < 2e19/cm 3 , resulting in the onset of Schottky behavior, (ii) Ohmic behavior between 3E19−7E19/cm 3 attributed to hole tunneling via field emission, whereas (iii) higher doping concentrations show a peculiar increase in resistivity due to deactivation of Mg but without any accompanying Schottky behavior in their I−V. 10 They propose this behavior to arise from tunneling through deep level defects and interfacial traps of compounds including accumulated Mg at the surface, via trap assisted tunneling, consistent with the high nonideality factors we observe. In comparison to many other studies, there is no annealing involved in our process.…”

Photoinduced entropy of InGaN/GaN p-i-n double-heterostructure nanowires

“…[16][17][18] Low NiO/p þ -GaN contact resistance can be realized thanks to hole tunneling through the potential barrier at the NiO/p þ -GaN interface, which significantly enhances the energy-saving performance of GaN-based p-i-n power devices. 19 High-level injection nitride-based p-i-n junction nanowires are suitable for attenuators, high-frequency switches, as well as photodetector applications. 20 However, non-radiative surface recombination and the filling of innershell vacancies affect the performance of devices based on such nanowires because the quantum efficiency of nanowire optoelectronic devices can be limited by the non-radiative Shockley-Read-Hall (SRH) 21 and Auger 22 recombination processes.…”