Improved Ohmic contact to GaN and AlGaN/GaN two‐dimensional electron gas using trap assisted tunneling by B implantation

Abstract

We have demonstrated that deep level traps created by B implantation can reduce the contact resistance by forming an additional path for electron transport via trap assisted tunneling in GaN and AlGaN/GaN heterostructures. B implantation by plasma‐immersion ion implantation creates deep level traps 0.36 eV below the conduction band edge to a shallow depth (10–25 nm) in the structure. These traps act as efficient percolation path for electrons between the TiN Ohmic contact and the active region, which can be bulk GaN or a two‐dimensional electron gas (2DEG) formed at the AlGaN/GaN heterostructure. The improved Ohmic behavior is manifested as reduced specific contact resistivity and normalized contact resistance. The specific contact resistance and the normalized contact resistance are found to decrease by 59% (30%) and 86% (51%), respectively, for bulk GaN (AlGaN/GaN). The effect of B implantation on the sheet resistance of the 2DEG is insignificant when the implantation energy and post‐implantation annealing time are controlled optimally.

Mechanism of Ti/Al/Ni/Au ohmic contacts to AlGaN/GaN heterostructures via laser annealing

“…As a result, an additional path is formed for electron transport via trap assisted tunneling in AlGaN/GaN heterostructures. [30] Therefore, the current transport mechanism of LA sample is dominated by TFE. According to our description, a schematic of the energy band diagram is shown in Fig.…”

Ohmic Contact to n-GaN Using RT-Sputtered GaN:O

“…As an alternative to the method described above, the selective ion implantation of donor dopants [ 7 , 8 ] or epitaxial growth (regrowth) of a highly-doped n + -GaN sub-contact layer in the recessed contact regions [ 9 , 10 , 11 ] are used to form ohmic contacts. To locally increase the donor doping in these regions, Si atoms are the element of choice, with a high solubility in GaN of the order of 10 20 cm −3 and a carrier concentration in the range 10 17 –10 19 cm −3 [ 12 ].…”

On the recovery of 2DEG properties in vertically ordered h-BN deposited AlGaN/GaN heterostructures on Si substrate

“…Penetration into the heterostructure causes significant deterioration of the 2DEG mobility due to scattering as well as increasing leakage current via trap assisted tunneling. 27) The sputtering related damage during the deposition of the h-BN on AlGaN/GaN HS has been recovered by a post-deposition annealing process (see Fig. 4).…”