Thermoelectric and micro-Raman measurements of carrier density and mobility in heavily Si-doped GaN wires

Abstract

International audienceCombined thermoelectric-resistivity measurements and micro-Raman experiments have been performed on single heavily Si-doped GaN wires. In both approaches, similar carrier concentration and mobility were determined taking into account the non-parabolicity of the conduction band. The unique high conductivity of Si-doped GaN wires is explained by a mobility µ=56 cm2 /V s at a carrier concentration n = 2.6 10^20 /cm 3. This is attributed to a more efficient dopant incorporation in Si-doped GaN microwires as compared to Si-doped GaN planar layers. (c) 2013 AIP Publishing LLC

Spectroscopic XPEEM of highly conductive SI-doped GaN wires

“…The resulting, hexagonal-shaped (side length $ 1.5 mm) wire was 20 mm long, with an n þ þ zone extending over $10 mm. Electrical measurements on the n þ þ zone of the wires revealed resistivities as low as 0.37 mΩ cm, which correspond to an electron density n ¼2-4 Â 10 20 at cm À 3 [1,4] . The axial doping distribution and uniformity over each zone was checked by means of Scanning Capacitance Microscopy (SCM) and Scanning Auger Microscopy (SAM) performed on the same wire.…”

“…It is desirable therefore to consider complementary, suitable contactless methods in the study of doped semiconducting wires able to provide direct insights on the doping properties. Here, we have employed a combination of surface-sensitive techniques based on X-ray photoelectron emission microscopy (XPEEM) to study the doping of highlyconductive [1,4], GaN microwires and complement bulk-sensitive electrical data. These objects are of high interest in solid-state lighting [5] and direct measurements regarding doping using physical characterization methods are desirable on single wires.…”

Carrier-induced refractive index change observed by a whispering gallery mode shift in GaN microrods

“…The analysis of WGMs from microrod structures have already been used to determine the refractive index of GaN [8]. In such microrods, high carrier concentrations above 2 × 10 20 cm −3 have been reported [9]. High carrier concentrations might modify the refractive index as it has been proposed in [10].…”

Phonon–plasmon coupling in Si doped GaN nanowires

“…These difficulties are specially arduous when dealing with self organized NWs grown by molecular beam epitaxy (MBE), where typical dimensions do not exceed 2-3 µm in length and 20-200 nm in radius [5]. Taking into account these constraints, several optical tools not requiring special sample preparation, such as photoluminescence [6,7] or Raman scattering [8,9] have provided the determination of carrier concentration. Compared to photoluminescence, Raman scattering experiments are usually performed at room temperature and may as well deliver information about size, structure, local density, strain or crystallographic orientation [10].…”

“…Compared to photoluminescence, Raman scattering experiments are usually performed at room temperature and may as well deliver information about size, structure, local density, strain or crystallographic orientation [10]. The use of this technique for the study of NW doping is however often hindered by the difficult detection of the phonon-plasmon coupled modes (LPP + , LPP − ) due to the presence of peaks from the substrate or to the over-damping of the plasmon modes [5,9].…”