Ohmic Contact to p-Type GaN Enabled by Post-Growth Diffusion of Magnesium

Abstract

We demonstrated the formation of excellent 1 Ohmic contact to p-type GaN (including the plasma 2 etching-damaged p-type GaN which otherwise exhibited 3 undetectable current within ±5V) by the post-growth 4 diffusion of magnesium. The specific contact resistivity 5 on the order of 10 -4 Ω.cm 2 (extracted at V=0V) was 6 achieved on the plasma-damaged p-GaN with linear 7 current-voltage characteristics by the transfer length 8 method (TLM) measurement. The improvement in current 9 by a factor of over 10 9 was also obtained on the plasma-10 damaged p-n junction diode after the same Mg-treatment.

Highly Scaled GaN Complementary Technology on a Silicon Substrate

“…This phenomenon is attributed to several reasons, mainly related to the characteristics of the p-FET: 1) Schottky turn-on behavior of the p-FET and 2) significant field-induced acceptor ionization at high gate overdrives and highly negative drain biases, in particular for the FinFET structure, as explained in Section II-B. Finally, it should be acknowledged that, significant research remains to be done in the co-optimization of this emerging GaN CT in the following: 1) further advancement of various process modules, e.g., ohmic contacts with low contact resistance [44], [45], [46] and low damage gate recess [25], [28]); 2) device and process engineering to achieve a good balance of performance specifications (DC and switching characteristics); and 3) epitaxial structure, to achieve lower channel resistances while ensuring carrier confinement.…”

Development of Low-Resistance Ohmic Contacts with Bilayer NiO/Al-Doped ZnO Thin Films to p-type GaN

“…Contacts with transparent conductive oxides such as Sn-doped In 2 O 3 (ITO) and Al-doped ZnO (AZO) have been developed, with AZO being more appealing than ITO as it is more environmentally friendly and cheaper, as well as having better electrical and optical properties . Nonetheless, AZO electrodes directly on p-GaN do not give the best performance, with I–V curves showing nonlinear characteristics or high specific contact resistances (ρ c ). , Hence, different interlayers such as Ni, − Pt, , ITO, , or Ag , have been used for Ohmic contacts to p-GaN.…”

Substitutional diffusion of Mg into GaN from GaN/Mg mixture

“…Region I shows a similar Mg distribution to the MgGaN layer, which is annealed at 800 °C for 5 min in Ref. 26. Therefore, region I is considered to be the MgGaN layer or region strongly affected by the MgGaN layer.…”

“…As a Mg-diffusion source that has these factors, we focus on a GaN/Mg mixture (MgGaN) layer, which is formed by annealing Mg deposited on GaN at about 800 °C in nitrogen atmosphere. 25,26) During this annealing, not only Mg diffuses from the Mg layer into the GaN layer, but Ga also diffuses from the GaN layer into the Mg layer. 25) This suggests that Ga vacancies are introduced into the GaN layer.…”

“…25) This suggests that Ga vacancies are introduced into the GaN layer. According to Wang et al, most of the Mg that diffused into the GaN layer is not activated, 26) but if the diffusion temperature is further increased, the Mg in the introduced Ga vacancies is likely to be activated; fortunately, the diffusion temperature can be easily increased by depositing a protective film such as AlN on MgGaN. In this paper, we report the Mg diffusion process for p-type GaN formation using MgGaN and the evaluation of Mg-diffused GaN.…”