Improved p-type conductivity in Al-rich AlGaN using multidimensional Mg-doped superlattices

Abstract

A novel multidimensional Mg-doped superlattice (SL) is proposed to enhance vertical hole conductivity in conventional Mg-doped AlGaN SL which generally suffers from large potential barrier for holes. Electronic structure calculations within the first-principle theoretical framework indicate that the densities of states (DOS) of the valence band nearby the Fermi level are more delocalized along the c-axis than that in conventional SL, and the potential barrier significantly decreases. Hole concentration is greatly enhanced in the barrier of multidimensional SL. Detailed comparisons of partial charges and decomposed DOS reveal that the improvement of vertical conductance may be ascribed to the stronger pz hybridization between Mg and N. Based on the theoretical analysis, highly conductive p-type multidimensional Al0.63Ga0.37N/Al0.51Ga0.49N SLs are grown with identified steps via metalorganic vapor-phase epitaxy. The hole concentration reaches up to 3.5 × 1018 cm−3, while the corresponding resistivity reduces to 0.7 Ω cm at room temperature, which is tens times improvement in conductivity compared with that of conventional SLs. High hole concentration can be maintained even at 100 K. High p-type conductivity in Al-rich structural material is an important step for the future design of superior AlGaN-based deep ultraviolet devices.

Impact of implantation geometry and fluence on structural properties of AlxGa1-xN implanted with thulium

“…Technological advances in crystal growth showed that problems like the solubility limit, hydrogen passivation, and high defect ionization energies, hampering p-type conduction, can be overcome to some extent. [5][6][7] Doping by ion implantation offers several advantages over doping during growth especially for selective area doping as reported by Tadjer et al 8 Furthermore, the present generation of "white" LEDs, using a phosphor, suffers from efficiency problems. Recently, Lim et al proposed a phosphor-free white LED based on threedimensional gallium nitride structures.…”

Experimental evidences for reducing Mg activation energy in high Al-content AlGaN alloy by MgGa δ doping in (AlN)m/(GaN)n superlattice

“…In this way, the Mg acceptor activation energy can significantly be reduced to 0.26 eV, very close to that of GaN, in (AlN) 5 /(GaN) 1 SL by Mg Ga δ-doping 1 . Recently, improved p-type conductivity was achieved in multidimensional Al 0.63 Ga 0.37 N/Al 0.51 Ga 0.49 N SLs 33 . In this work, we use Mg Ga δ doping in (AlN) m /(GaN) n SLs to study Mg acceptor activation energy, aiming to find a proper way to minimize it in high Al-content AlGaN.…”

P-type silicon as hole supplier for nitride-based UVC LEDs

“…To improve the free hole concentration in high-Al content AlGaN materials, researchers have developed the approach of polarization doping [6][7][8][9][10] for the purpose of enhancing electrical conductivity. By linearly grading the Al composition of AlGaN, the polarization bound charge spreads to a 3D form and induces the formation of a mobile 3D carrier gas of the opposite charge, resulting in an increased carrier concentration [11][12][13][14][15] over impurity doping.…”