Investigation of Mg δ-doping for low resistance N-polar p-GaN films grown at reduced temperatures by MOCVD

Abstract

In this study we explored p-type δ-doping for the deposition of N-polar p-GaN films at 900 °C, for application in device structures containing high In composition active layers. Various δdoping process parameters were investigated, including the duration and molar flow of the Mg precursor during each pulse as well as the δ-doping period. The results were compared to those obtained for layers grown using continuous doping. As the δ-doping period was reduced from 25 to 5 nm, the p-GaN bulk resistivity decreased from 6.8 to 2.8 W cm. The p-layer resistivity rose with increasing [Mg] independent of the doping scheme. For similar average [Mg], however, continuous doping resulted in a lower resistivity compared to δ-doping. This effect was more pronounced at higher [Mg], indicating that high local concentrations of Mg resulted in degradation of the electrical performance. After optimization of the p-layer structure and contact fabrication process, a minimum contact resistance of 2.77 mW cm 2 and a minimum resistivity of 1.33 W cm were achieved.

Hillock assisted p-type enhancement in N-polar GaN:Mg films grown by MOCVD

“…Additionally, the N-polarity suffers from a high concentration of unintentionally incorporated oxygen (compared to the Ga-polarity), which compensates free holes 21 . Progress has been made in partially overcoming these challenges through the use of delta doping in both the Ga-and N-polarity [22][23][24] to enhance p-conductivity. Both calcium 25 and zinc [26][27][28][29][30] have been explored as alternative acceptors in GaN however, the ionization energies in both dopant species have been shown to be similar or higher compared to magnesium.…”

Selectively dry etched of p-GaN/InAlN heterostructures using BCI3-based plasma for normally-off HEMT technology

“…When figure 6 is examined, it is seen that the surface roughness decreases depending on the etching time. We think that this is due to induce the surface modification and also changed the particle size on the surface with respect to the etching time increases in our recipe, which is mostly chemical etching [14][15][16][17][18][19][20][21][22][23][24][25][26][27].…”

All-MOCVD-grown gallium nitride diodes with ultra-low resistance tunnel junctions

“…Introducing a delta (δ) dose at the doped layer interfaces has also proven to be effective [17][18][19]. Compared to a continuously doped layer, the δ-dose layer shows an order of magnitude higher carrier concentration.…”