Use of nitrogen as a carrier gas in LP-MOCVD for growth of GaAs AlGaAs and quantum well infrared photodetectors heterostructures

Abstract

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 ...