Growth and characterization of N‐polar GaN and AlGaN/GaN HEMTs on (111) silicon

Abstract

Smooth, high quality N‐polar GaN‐on‐silicon films with treading dislocation densities comparable to Ga‐polar GaN‐on‐Si films and N‐polar GaN/AlGaN/GaN transistors were demonstrated by metal‐organic chemical vapour deposition on (111) Si substrates misoriented 3.5° toward [11$ \bar 2 $]. The N‐polarity was established through high magnesium doping during deposition of the AlGaN strain management layers. The results encourage future exploration of N‐polar (Al,Ga,In)N‐on‐silicon hetero‐structures. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

N-polar GaN epitaxy and high electron mobility transistors

“…Strategies to nucleate N-polar materials on Si by PAMBE include substrate nitridation to form SiN x followed by nucleation under N-rich conditions [225,226], or controlled deposition of Al metal on Si prior to growth initiation [227]. The first N-polar transistors on Si substrates are demonstrated with MOCVD on misoriented Si (1 1 1) by inverting a Ga-polar film to N-polar [228,229]. Si substrates with a miscut of 3.5 • toward [11 2] or [1 1 0] are investigated.…”

“…To avoid any impact of the Mg doping on device performance, Mg-doped layers and active device layers have to be separated by an undoped spacer layer with a thickness in excess of 600 nm. The optimum Si substrate misorentation direction is [11 2], resulting in GaN films misoriented toward the m-plane with smooth surfaces and a regular step structure [229]. Room temperature electron mobility values of 1508 cm 2 V −1 s −1 and 1760 cm 2 V −1 s −1 parallel to the step direction are measured for samples with sheet carrier densities of 9.6 × 10 12 cm −2 and 6.3 × 10 12 cm −2 , respectively, in the absence of a mobilityenhancing AlN interlayer between the AlGaN back-barrier and the GaN channel [228].…”

Study of dry etched N-polar (Al)GaN surfaces obtained by inductively coupled plasma etching

“…The wafer bow was controlled within ±20 μm. It should be noted that the GaN polarity in the MOVPE growth on a Si <111> substrate is preferentially Ga-polar unless with intentional polarity inversion process [27]. Therefore, the bottom side of the epi-layer must be N-polarity.…”

Polarity Inversion of Ga‐Polar GaN Surfaces by Exposing to Mg and NH3 in Metal–Organic Vapor Phase Epitaxy

“…[7][8][9][10] N-polar highelectron-mobility transistors have been developed on Si (111) substrates by polarity inversion on a Ga-polar template. [11] In general, the polarity inversion from N-to Ga-polar can be achieved by multiple approaches such as insertion of a metallic bilayer, [12] an AlN or aluminum oxide interlayer, [13,14] and a heavy doping of Mg. [5,15] However, the inversion from Ga-to N-polar is relatively challenging. In the metal-organic vapor phase epitaxy (MOVPE) process, heavy Mg doping (≈10 20 cm −3 ) in the GaN growth is the main method reported in the literature for Ga-to N-polarity inversion.…”

“…In the metal-organic vapor phase epitaxy (MOVPE) process, heavy Mg doping (≈10 20 cm −3 ) in the GaN growth is the main method reported in the literature for Ga-to N-polarity inversion. [11,16,17] In this work, we report an alternative MOVPE process of polarity inversion from Ga-to N-polar by exposing the Ga-polar surface in a mixed flow of Mg and ammonia (NH 3 ). The polarity of a GaN overlayer on such a Ga-polar surface can be fully inverted to N-polar by controlling the exposure time and temperature.…”