Some benefits of Fe doped less dislocated GaN templates for AlGaN/GaN HEMTs grown by MOVPE

Abstract

Strategies for maintaining a low threading dislocation density in highly resistive GaN layers grown by MOVPE on sapphire or SiC substrates using Fe modulation doping are presented. Sheet resistances as high as 108 Ω□ for dislocation densities lower than 8 × 108 cm–2 have been obtained. 2DEGs created at the AlGaN/GaN:Fe interface have good confinement while the low dislocation density benefits the mobility: room temperature values up to 2170 cm2 V–1 s–1 have been obtained for a carrier density of 9.3 × 1012 cm–2. A simplified transport model is proposed to fit the experimental data. Processed transistors showed good channel control and DC performance. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

On the incorporation mechanism of Fe in GaN grown by metal‐organic vapour phase epitaxy

“…Surface roughening was also reported by Heikman et al for their highest doping level [13]. Indeed, Bougrioua et al have demonstrated a novel method for dislocation reduction by intentionally promoting 3D growth by introducing a short period of high Fe doping, followed by a slow coalescence recovery to a 2D growth mode [11]. …”

Inhibition of interface pollution in AlGaN/GaN HEMT structures regrown on semi-insulating GaN templates

“…SI templates (noted GaN:Fe-MD) were grown following procedure presented in Refs. [2,6]. Aluminium content used for AlGaN supply layers was in the range 18-26%.…”

The Spatial Distribution of Threading Dislocations in Gallium Nitride Films

“…High TD densities increase the leakage currents in blue and green LEDs, [6] decrease the lifetime of laser diodes, [7] reduce the efficiency of near-UV LEDs [8] and lower electron mobilities in HEMTs. [9] TDs might also be at least partly responsible for the reduced internal quantum efficiency which is typical of greenand yellow-emitting InGaN-based LEDs (the 'green gap'). Furthermore, TDs are known to cause premature junction breakdown and may prevent high gains and low dark currents from being reached in GaN-based UV avalanche photodiodes; [10,11] they can also cause current collapse in GaN-based field-effect transistors used in RF applications [12] and are generally detrimental to the performance of high-power GaN-based devices.…”