Session: AM9.1 - Materials for (strategic sectors) Aerospace and Defense applications

Paper Number: 188784

188784 - Effect of Laser Assisted Doping on Piezoresistance of Semi-Insulating 4h-Silicone Carbide 

Silicon carbide (SiC) is a wide bandgap (2.3 – 3.2 eV) semiconductor with good mechanical properties, electrical breakdown strength and chemical resistance. In particular, there is growing interest in developing 4H-SiC as a piezoresistive sensor for applications that require functional electronic devices operating in harsh and high-temperature environments. Laser-assisted doping of semi-insulating silicon carbide (SiC) is challenging due to its chemical inertness and low diffusion coefficient. In this work, a single-crystal semi-insulating 4H-SiC substrate with a thickness of 500 µm is doped with aluminium (Al) and phosphorous (P) using a neodymium-doped yttrium aluminium garnet (Nd³⁺:YAG) laser with a wavelength of 266 nm. A selective-area, maskless doping technique was used to irradiate the 4H-SiC substrate with the Nd³⁺:YAG laser, using different liquid dopant sources and Al and P doping concentrations of 10¹⁶ cm^-3 and 10²² cm^-3, respectively. The diffusion profile of the dopants estimated by secondary ion mass spectroscopy (SIMS) shows substitutional diffusion near the surface, up to 200 nm depth, and interstitial diffusion up to 1 µm depth. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies qualitatively show diffusion of dopant, represented by peak shifts in XRD and changes in the ‘c’ lattice parameter, as estimated from electron diffraction spot patterns using the TEM studies. To measure piezoresistive characteristics, a SiC substrate (100 mm long × 10 mm wide) was doped with both Al and P sequentially in a 4 mm × 0.5 mm area at one end. The doped SiC substrate was metallized, wire-bonded and fixed to form a cantilever beam. The response, in terms of change in resistance to strain induced by a known displacement at the free end of the cantilever, was measured to estimate the gauge factor (GF). The gauge factor (GF) of the SiC was estimated at room temperature to be 10.5 when doped with Al and 15.6 when doped with P. The proposed laser-assisted maskless selective-area doping of semi-insulating 4H-SiC is suitable for piezoresistive sensor applications.

Presenting Author: SREE HARSHA CHOUTAPALLI INDIAN INSTITUTE OF TECHNOLOGY MADRAS

Presenting Author Biography: Sree Harsha works silicon carbide technology aimed at semi-conductor applications. His research includes pulsed laser deposition of silicon carbide thin films, and laser assisted doping of silicon carbide substrates and thin films and substrates with both p-type and n-type dopants.