Investigation of nitrogen polar p-type doped GaN/AlxGa(1-x)N superlattices for applications in wide-bandgap p-type field effect transistors

TL;DR

This paper explores N-polar GaN/AlGaN superlattices grown via MOCVD, demonstrating high hole mobility and density, and fabricates test transistors to evaluate their potential in wide-bandgap p-type FET applications.

Contribution

It presents the growth and electrical characterization of N-polar modulation doped GaN/AlGaN superlattices, showing improved hole mobility and device performance for wide-bandgap transistors.

Findings

Hole mobility up to 18 cm²/Vs at high hole density

High hole sheet charge density of 6.5e13 cm⁻²

Test transistors show promising current capabilities

Abstract

In this study the MOCVD growth and electrical properties of N-polar modulation doped p-AlGaN/GaN superlattices (SLs) were investigated. Hole sheet charge density and mobility were studied as a function of the concentration of the p-type dopant Mg in the SL and the number of SL periods. Room temperature Hall measurements were carried out to determine the hole mobility and the sheet charge density. While the hole density increased with increasing number of SL periods, the hole mobility was largely unaffected.Hole mobilities as high as 18cm2/Vs at a simultaneous high hole density of 6.5e13 cm-2 were observed for N-polar SLs with a Mg modulation doping of 7.5e18 cm-3. For comparable uniformly doped Ga-polar SL samples, a mobility of 11cm2/Vs was measured. Lowest sheet resistance in the GaN/AlGaN materials system of 5kOhm/sq is also reported. Test-structure transistors were also fabricated to investigate the applicability of these SL structures, with planar device resulting in a current of 5mA/mm, and a FinFET structure resulting in a current of over 100mA/mm.