Doping and compensation in Al-rich AlGaN grown on single crystal AlN and sapphire by MOCVD

Abstract

In order to understand the influence of dislocations on doping and compensation in Al-rich AlGaN, thin films were grown by metal organic chemical vapor deposition (MOCVD) on different templates on sapphire and low dislocation density single crystalline AlN. AlGaN grown on AlN exhibited the highest conductivity, carrier concentration, and mobility for any doping concentration due to low threading dislocation related compensation and reduced self-compensation. The onset of self-compensation, i.e., the “knee behavior” in conductivity, was found to depend only on the chemical potential of silicon, strongly indicating the cation vacancy complex with Si as the source of self-compensation. However, the magnitude of self-compensation was found to increase with an increase in dislocation density, and consequently, AlGaN grown on AlN substrates demonstrated higher conductivity over the entire doping range.

Improved Efficiency of Ultraviolet B Light‐Emitting Diodes with Optimized p‐Side

“…[ 22,24 ] As the dislocations represent traps for holes, they can also reduce p‐conductivity of the SLs. [ 12,32 ] In addition, due to the large thickness and composition fluctuations of the SL layers, the enhanced ionization of the magnesium acceptors by polarization fields doesn't take place which destroys the possibly better conductivity of a SL. Therefore, for further investigations of the p‐side design, the p‐doped SL in the 310 nm LEDs was replaced by a p‐ bulk layer.…”

Electrical properties of (11-22) Si:AlGaN layers at high Al contents grown by metal-organic vapor phase epitaxy

“…This trend is described in the literature as "knee-like behavior", being observed for AlGaN:Si with high aluminum mole fractions [30,33,34]. The mobility of 20 -24 cm 2 V -1 s -1 measured here resembles the value for high dislocation density (~mid 10 10 cm -3 ) c-plane Si:Al0.7Ga0.3N [33], which indicates that mobility is independent of the growth plane for materials with a high defect density, as also the samples investigated here exhibit a high dislocation density in the range of 10 10 -10 11 cm -2 [23,24] indicated by the FWHM of the symmetric (11-22) reflex which was equal for all samples of 900" and 1800" with incidence along [11-2-3] and , respectively.…”

BAlGaN alloys nearly lattice-matched to AlN for efficient UV LEDs

“…We find that partial replacement of aluminum by single-digit percent boron in AlGaN alloys has negligible effect on the band gap, and causes a large reduction in the a lattice constant to match that of AlN. Lattice matching to AlN allows device designs that take advantage of the low TDD (~10 3 -10 4 cm -2 ) 9) of AlN substrates, greatly reducing Shockley-Read-Hall losses and improving the internal quantum efficiency. Our thermodynamics analysis reveals that alloys at the studied compositions can readily be grown, allowing for the growth of BAlGaN layers lattice-matched to AlGaN that emit in the 6.03 -4.19 eV (206-296 nm) range.…”