Paper TF1-ThA10
Optical Characterezation of InN layers grown by High-Pressure CVD

Thursday, October 18, 2007, 5:00 pm, Room 602/603

A growing number of potential applications such as high-efficient heterojunction solar cells,thermoelectric devices and terahertz detector will become possible as Indium Nitride (InN) and In-rich group III-nitride(N) materials become more mature and can be integrated with other-rich group III-N alloys. Understanding and controlling the physical properties of the InN is of essential importance next to its integration as a component of (Ga_1-xIn_x)N alloy system, which is crucial for fabrication of wavelength tailored high-efficient LEDs and displays. The present limitations in this area are in the growth of high quality InN and In-rich group III-N at processing conditions that are compatible with GaAlN aloys.The difficulties arise from the low dissociation temperature of In-rich groupIII-N, requiring extraordinarily high nitrogen overpressure to stabilize the material up to optimum growth temperatures. Our research explores the growth of InN and In-rich group III-N by high-pressure chemical vapor deposition (HPCVD), an approach that allows controlling and stabilizing the vast different partial pressures of the constituents. The results show that the chosen HPCVD pathway leads to high-quality single crystalline InN, demonstrating that HPCVD is a viable tool for the growth of In-rich III-N alloys. The structural analysis of InN deposited on GaN-Sapphire substrate by XRD show single phase InN(0002) peaks with full width half maximum below 400 arcsec. The optical transmission analysis shows that an apparent band gap is around 1.4 eV with absorption centers at 0.8 eV and 0.4 eV. The strength of the low energetic absorption centers are closely related to the precursor ratios and the utilized growth temperatures. Infrared reflectance spectroscopy is used to estimate the high frequency dielectric constant, the free carrier concentrations and carrier mobilities in these layers. The free carrier concentration is found to be in the upper 10¹⁹ cm^-3 with the corresponding mobilities around 600 cm⁺²V^-1s^-1.A further reduction of residual extrinsic impurities in the precursor and carrier gas is presently explored to further reduce the free carrier concentration in the layers.The modeling of the IR-reflectance spectra indicate the present of two distinct InN layers: one with electron concentrations below 5x10¹⁷cm^-3,which is followed by second layer in the upper 10¹⁹cm^-3 closer to the surface.