Heavily Si-doped pulsed sputtering deposited GaN for tunneling junction contacts in UV-A light emitting diodes

Abstract

We report the characteristics of heavily Si-doped GaN prepared by pulsed sputtering deposition (PSD) and its application as tunneling junction (TJ) contacts for nitride-based light-emitting diodes (LEDs). We determined that the use of PSD allows us to grow extremely heavily Si-doped wurtzite GaN epitaxial layers with [Si] = 1.0 × 1021 cm−3 on commercially available UV-A LED wafers. Then, we processed these samples into LED structures to investigate their device characteristics as TJ-contact LEDs. Compared to commercially available UV-A LEDs with transparent conductive oxide contacts, TJ-contact LEDs with [Si] = 1.0 × 1021 cm−3 at the tunnel-junction interface showed lower differential resistance and, consequently, worked well under a high injection current density of ∼1 kA/cm2 without any degradation. These results indicate that PSD-grown heavily doped n-type GaN is promising for application as a TJ-contact in group III nitride-based optoelectronic devices.

Mid-infrared thermal radiation resonating with longitudinal-optical like phonon from n++-doped GaN–semi-insulating GaN grating structure

“…The imperfect interface induces a smaller amount of coherently vibrating interface polarization charges, resulting in a minor electric dipole moment and the lower energy shift of the dipole stemming from the original LO-phonon energy (D 3 in the model in section 3.1). In contrast, according to Fudetani et al [41], the high-resolution TEM image shows a good interface between p-GaN and n ++ -GaN, with no defects identified. These results reveal that the interface condition affects the peak position and emission intensity.…”

Pulsed sputtering growth of heavily Si-doped GaN (20 2̄ 1) for tunneling junction contacts on semipolar InGaN (20 2̄ 1) LEDs

“…This value was as low as that for the c-plane. 20) These results indicate that the use of PSD enabled the formation of TJ contacts on the (202 ̄1) LED wafers with abrupt doping profiles and high structural perfection.…”

“…The PSD TJ contacts on UV-A InGaN (0001) LEDs work well with a low turn-on voltage and differential resistance. 20) In addition, the doping efficiency in PSD seems to be less sensitive to crystallographic orientation compared to the case of conventional metal-organic vapor deposition (MOCVD) because the PSD growth proceeds in highly nonequilibrium nitrogen plasma at lower growth temperatures. Thus, the PSD technique potentially provides an excellent opportunity to investigate the characteristics of heavily doped GaN and TJs on non-c-planes.…”

“…The growth conditions were identical to those of c-plane growth reported previously in the literature. 16,20) The TJ contacts consisted of 600 nm thick n + -GaN ([Si] = 4 × 10 19 cm −3 )/50 nm thick n ++ -GaN ([Si] = 1 × 10 21 cm −3 ) stacks on the green (202 ̄1) LED. Then, the TJ contact (202 ̄1) LED wafers were processed into mesa structures as defined by photolithography and inductively coupled plasma etching.…”

Pulsed sputtering selective epitaxial formation of highly degenerate n-type GaN ohmic contacts for GaN HEMT applications

“…30) We discovered that Ge-doping and Sn-doping in GaN via PSD led to the formation of highly n-type doped GaN, with electron concentrations exceeding 10 20 cm −3 . 31,32) This highly n-type doped degenerate GaN (d-GaN) performed effectively as low-resistive tunneling junction contacts in UV-A LEDs 33) and in the tunneling-junction-based interconnection of cascaded LED structures. 34) Given these excellent electrical properties of d-GaN and the nature of PSD, which is wellsuited for large-area and high-throughput epitaxial growth, we believe that exploring the selective epitaxial formation process of d-GaN ohmic contacts for HEMT applications is a worthwhile endeavor.…”