Influences Of Silicon Doping And In-situ SiN_x Interlayer On The Optical And Electrical Properties Of Nonpolar A-plane GaN

In this article,high-quality non-polar ?-plane GaN single-crystal thin films with different Si doping concentrations and with or without an in-situ SiNx interlayer were grown on the r-plane sapphire using metal-organic chemical vapor deposition equipment.A variety of characterization and analysis methods were used to study the influences of silicon doping and SiNx interlayer on the optical and electrical properties of non-polar ?-plane GaN,which provides valuable results for the manufacture of high-performance non-polar ?-plane GaN-based devicesThe major works conducted in this research are listed as follows(1)The electrical and optical properties of a series of non-polar ?-plane GaN grown with different SiH4 flow rates were systematically studied using temperature-dependent Hall and photoluminescence.For the flow rate of in-situ SiH4 less than 16.06 nmol/min,the mobility of electron Hall increased with the increase of the flow rate of SiH4,but it decreased with the increase of the flow rate of SiH4 when the flow rate of SiH4 was larger than 16.06 nmol/min.Meanwhile,the sample's primary scattering mechanism with a SiH4 flow rate of 16.06 nmol/min changed with temperature,and it was ionized impurity scattering below 450 K and thermal lattice vibration scattering above 450 K.XPS analysis and infrared absorption spectrum suggested that this phenomenon could attribute to the more disordered lattice vibration caused by silicon doping.Besides,photoluminescence spectra(PL)indicated that silicon doping could reduce the densities of basal-plane stacking faults(BSFs)and Ga vacancies and increase the electron Hall mobility of the sample.High-resolution X-ray diffraction(HRXRD)measurements revealed that,compared with the undoped sample,the density of BSFs of silicon-doped ?-plane GaN with a silane flow rate of 16.06 nmol/min reduced by 12.02%(2)The influence of the in-situ SiNx interlayer on the surface morphology,crystal structure,electrical and optical properties of the nonpolar GaN epitaxial layer were thoroughly studied.The Hall mobility of nonpolar ?-plane GaN increased from 6.64 cm2/V·s without in-situ SiNx layer to 68.68 cm2/V·s with in-situ SiNx layer.Compared with ?-plane GaN without a in-situ SiNx interlayer,the surface defects and the roughness RMS of ?-plane GaN with a in-situ SiNx interlayer were reduced by 83%and 61%,respectively.Low-temperature photoluminescence spectroscopy(LTPL)measurement revealed that the fluorescence radiation related to BSFs was also significantly suppressed.The HRXRD measurement demonstrated that after inserting the SiNx layer,the density of BSFs decreased from 1.83×105 to 8.13×104 cm-1,which proved in-situ SiNx layers can effectively prevent BSFs in nonpolar GaN from continuing to propagate upward.Therefore,it can be inferred that the reduction in the density of BSFs and surface defects,as well as the improvement in surface roughness,contributed the improving the Hall mobility of samples containing in-situ SiNx layer.Meanwhile,time-resolved photoluminescence spectroscopy(TRPL)manifested that the rapid decay process's lifetime increased from 16.2 ps to 71.1 ps,indicating that after the in-situ SiNx layer was inserted,the non-radiative recombination in nonpolar GaN was also significantly suppressed.Finally,Raman spectroscopy demonstrated that the in-situ SiNx interlayer reduces the strain of ?-plane GaN along the directions of [1(?)00] and [0001] axes by 58.9%and 78.0%,respectively.