The a-GaN films were successfully grown on the r-sapphire substrate by MOCVD method. The structure of V-defects was investigated by AFM and SEM. The dependence of V-defects density on growth temperature of a-GaN film at a constant hydrogen flow through a TEG source was studied. The influence of V/III ratio on V-defects structure was investigated. Methods of V-defects density minimisation were purposed.
The n-type and p-type a-GaN films were successfully grown on a r-sapphire substrate, according to X-ray diffractometer and SEM results parameters measurement. The growth rate versus the growth temperature was investigated. The holes concentration (8x1017 cm−3) was achieved by the Cp2Mg flow optimization and the parameters of thermal annealing in nitrogen. The GaN film growth rate dependence versus temperature at a constant hydrogen flow through a TEG source was investigated. The results indicate that defects density is reduced upto 104 cm−2, the surface morphology uniformity was improved. During growth the influence from V/III flows ratio was detected.
The n‐type and p‐type a‐GaN films are successfully grown by MOCVD on the r‐sapphire substrate with smooth mirror surface morphology. The growth rate versus the growth temperature is investigated. Optimum doping parameters by acceptor and donor impurities − 8 × 1017 and 4 × 1018 cm−3 are determined. Low‐temperature amorphous buffer (nucleus) GaN layer and the island growth process with additional doping profile in quantum wells (QW) are investigated. The heterostructures are grown based on direct investigation and simulation results and are investigated by atomic‐force microscopy (AFM) and scanning electron microscopy (SEM). In this work, V‐defects of the structure for non‐polar orientation films are investigated for the first time, thus complementing earlier results for polar and semi‐polar films. The results indicate that the defect density was reduced up to 104 cm−2, with improved surface morphology uniformity. During growth, the influence from V/III flow ratio and doping barriers by indium atoms was detected. Decrease in the V/III ratio up to 1320 at the overgrowth stage of the precipitated low‐temperature nuclei caused growth‐island formation and increased the growth rate in the lateral direction, thus decreasing the dislocation density.
Investigation of the effect of crystal defects on nonpolar a-GaN films grown by metalorganic chemical vapor deposition on r-sapphire substrates is presented. Samples were grown at different temperatures and the same V/III ratio. High-temperature nucleation in combination with low-temperature GaN buffer layer growth was used to achieve a smooth morphology and “mirror” surface. The macrostructures of the defects were investigated using a scanning electron microscope. Defect concentration via dislocation type correlation was analyzed by diffractometry investigation. Structural quality was investigated via x-ray diffraction. The correlation between the densities of mixed threading dislocations and V-defects was determined. It was detected that the origin of V-defects on the a-plane and c-plane was the same despite having completely different geometries and structures. We also investigated the dependence of V-defect density on a-GaN film growth temperature at a constant hydrogen flow through a triethylgallium source, and we also investigated how the V/III ratio influenced the V-defect structure. Optimum growth parameters for defect concentration reduction were determined.
I. ABSTRACTIn this paper the growth of GaAs and A1GaAs metal organic chemical vapor deposition (MOCVD) when nitrogen is used as carrier gas instead of hydrogen have been investigated. Properties of epilayers were studied in dependence from such parameters of epitaxy process as V/Ill ratio in gas phase, susceptor temperature and pressure in reactor. We fixed a conductivity type conversion from n-to p-type when mole fraction of Al in A1GaAs was increased from 19% to 67%. The abroad of conversion is near 40%. The increasing of methyl-radicals from trimethylaluminium concentration is a possible reason of this fact.To demonstrate the possibility of device structure growth by , using in MOCVD nitrogen as carrier gas in first time the Quantum Well Infrared Photodetectors (QWIP) heterostructures have been fabricated. Some features of devices parameters are discussed.A device with mesa-structure has a dark current density of 1 . 106A at U2V and T771; the responsivity at U=2V and 45° angle incidence of JR-radiation was S0. 1A/W (2max =10.7 mkm). II. INTRODUCTIONRecently several authors reported about successful growth of GaAs layers with the using of nitrogen as a carrier gas in low pressure MOCVD [ 1] . Nitrogen has several advantages compare with hydrogen. They are: 1) less dangerous in epitaxy process and further treatment of exhaust gases; 2) the quasi laminar flow is more easy to achieve; 3) to achieve a high level of p-type doping in wide gap materials (like as A1GaInP and GaN and related compounds) it is necessary to solve problems concern with hydrogen presence. This problem is absent when nitrogen is used.In [2] it was reported that morfology and photolurninescence of InP and InGaAs was increased by using of H+N mixture.The quality of barrier material in QWIP-structures is most important. In [3] it was demonstrated that parameters of photodetectors were worse dramastically when growth temperature was decreased from 700 up to 625°C. The single explanation to this fact is strong increasing of deep levels in A1GaAs-barriers. In the same time in [4] it was reported that deep level concentration in A1GaAs was decreased when nitrogen was used. It was interesting to grow QWIP-structure by MOCVD nitrogen epitaxy as parameters of this photodetectors are critical to AJGaAs barrier quality. O-8194-1744-O/95/$6.OO SPIE Vol. 2397 / 733 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/24/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx III. EXPERIMENTAL PROCEDURE .The epitaxial growth experiments have been carried out on horizontal tube reactor with tube diameter 100 mm in standard low pressure MOCVD-system with IR-heating. The stable graphite susceptor was radiation heated and have a growth sizes 8Oxl2Omm. The angle between growth area and gas flow was varied from 0 to 12°. We use a special gas flow input laminator from stainless steel to achieve laminar conditions during epitaxial growth. To decrease a total moisture and oxygen contamination up to less than 1 ppm "Sigma Chem" superpurifier ...
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