Doping of GaN by Ion Implantation: Does it Work?

Abstract

SS.;5'Epitaxially grown GaN by metal organic chemical vapor deposition (MOCVD) on Si were implanted with 100 keV Si' (for n-type) and 80 keV Mg' (for p-type) with various fluences from 1 x 1 0l2 to 7x1 015 ions/cm2 at liquid nitrogen temperature (LT), room temperature (RT), and 700 O C (HT). High temperature (1200 O C and 1500 OC) annealing was carried out after capping the GaN with epitaxial AIN by MOCVD to study damage recovery. Samples were capped by a layer of AlN in order to protect the GaN surface during annealing. Effects of implant temperature, damage and dopant activation are critically studied to evaluate a role of ion implantation in doping of GaN. The damage was studied by Rutherford BackscatteringKhanneling, spectroscopic ellipsometry and photoluminescence. Results show dependence of radiation darnage level on temperature of the substrate during implantation: implantations at elevated temperatures up to 550 O C decrease the lattice disorder; "hot implants" above 550 O C can not be useful in doping of GaN due to nitrogen loss from the surface. SE measurements have indicated very high sensitivity to the implantation damage. PL measurements at LT of 80 keV Mg+ ( 5~1 0 '~ cm-2) implanted and annealed GaN showed two peaks : one -100 meV and another -140 meV away from the band edge.

Chemical origin of the yellow luminescence in GaN

“…The apparent recovery of detected luminescence by such annealing, which has been observed experimentally, 2,13,21,[45][46][47][48][49] has been attributed to ͑i͒ thermally induced recovery of lattice defects that enhance the absorption of light within the implanted layer and ͑ii͒ recovery of CL emission in the ion end-of-range region, where the concentration of implantation-produced defects is sufficiently low so that most of these defects can be effectively removed by such annealing. 49 Indeed, previous studies 49 have shown that CL emission is restored in the ion end-of-range region, where the level of implantation disorder is relatively low, but the concentration of implanted species is relatively high.…”

Effect of ion species on the accumulation of ion-beam damage inGaN

“…Recent ion-implantation studies [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] have revealed that, unlike the situation for mature semiconductors such as Si and GaAs, GaN exhibits a range of intriguing behavior involving extreme property changes under ion bombardment. 19 In particular, it has been shown that dynamic annealing processes ͑i.e., defect-interaction processes͒ in GaN are extremely efficient even during heavy-ion bombardment at liquid-nitrogen temperature.…”

Disordering and anomalous surface erosion of GaN during ion bombardment at elevated temperatures

“…Parikh et al 3 reported Rutherford backscattering/channeling ͑RBS/C͒ and crosssectional transmission electron microscopy ͑XTEM͒ studies of GaN bombarded with 120 keV Mg and 160 keV Si ions at 550°C. Suvkhanov et al 4 reported a RBS/C study of GaN bombarded at 700°C with 100 keV Si and 80 keV Mg ions. Another report on lattice disorder produced by a moderate dose of 90 keV Mg ions implanted into GaN at temperatures up to 550°C and studied by RBS/C was reported by Wenzel, Liu, and Rauschenbach.…”

“…After implantation, samples were characterized ex situ by RBS/C with 1.8 MeV 4 He ϩ ions incident along the ͓0001͔ direction and backscattered into a detector at 98°relative to the incident beam direction to provide enhanced depth resolution for examining near-surface damage accumulation. XTEM was performed in a Philips CM12 transmission electron microscope operating at 120 keV.…”