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Ankush Bag,Rahul Kumar,Partha Mukhopadhyay,Mihir K. Mahata,Apurba Chakraborty,Saptarsi Ghosh,Sanjay K. Jana,Dhrubes Biswas 대한금속·재료학회 2015 ELECTRONIC MATERIALS LETTERS Vol.11 No.4
In-situ RHEED and ex-situ AFM characterizations have been employed to investigate transformations of surface topography with the thickness of PAMBE grown AlGaN and InGaN on GaN. The ternary alloys have been grown with identical growth-front roughness as confirmed by XRR and RHEED observations. The spottier RHEED has been observed with increased thickness of the InGaN as opposed to streakier behavior of AlGaN. We have noticed incremental nature of RMS roughness, skewness and kurtosis of InGaN surface compared to GaN or AlGaN from AFM as evident by final spotty RHEED for InGaN. However, the analyzed fractal dimension is lower for InGaN as opposed to AlGaN ( ). From the kinetic roughening perspective of adatoms, the experimental evidences lead to the high correlation between binding energy of the cluster atoms ( ) and the modified DDA growth model with dissociation and evaporation to confirm the efficacy of the study. The initial streaky and spotty RHEED of InGaN and AlGaN, respectively, can be attributed to their Eb that causes smoothing and roughening of the GaN surface due to adatoms surface mobility behavior. Therefore, the fractal description reveals the fact during formation of nitride hetero-interface while other AFM results describe the top surface.
Rahul Kumar,Ankush Bag,Partha Mukhopadhyay,Subhashis Das,Dhrubes Biswas 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.3
There exist discrepancies between reports on cross-hatch (CH)behaviour and its interaction with interfacial misfit dislocations in theliterature. In this work, a thorough CH analysis has been presentedby use of conventional and statistical analysis of AFM data. It hasbeen shown that correlation between cross-hatch and misfitdislocation depends on the growth conditions and residual strain. Anisotropic relaxation and dislocations, composition and epitaxial tilthave been studied by HRXRD analysis. To illustrate these findings,molecular beam epitaxy (MBE) grown metamorphic InGaAs onGaAs (001) samples have been used. Reciprocal space mapping hasbeen used to characterize the composition and relaxation whileepilayer tilt and dislocation have been investigated by HRXRDrocking curve. A better understanding of CH pattern can enable us tominimize the surface roughness for metamorphic electronic devicesand to fully utilize the quasi-periodic undulation in cross-hatch inapplications, like ordered quantum dot growth.
Reverse Bias Leakage Current Mechanism of AlGaN/InGaN/GaN Heterostructure
Apurba Chakraborty,Saptarsi Ghosh,Partha Mukhopadhyay,Sanjay K. Jana,Syed Mukulika Dinara,Ankush Bag,Mihir K. Mahata,Rahul Kumar,Subhashis Das,Palash Das,Dhrubes Biswas 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.2
The reverse bias leakage current mechanism of AlGaN/InGaN/GaNheterostructure is investigated by current-voltage measurement intemperature range from 298 K to 423 K. The Higher electric field acrossthe AlGaN barrier layer of AlGaN/InGaN/GaN double heterostructuredue to higher polarization charge is found to be responsible for strongFowler-Nordheim (FN) tunnelling in the electric field higher than3.66 MV/cm. For electric field less than 3.56 MV/cm, the reverse biasleakage current is also found to follow the trap assisted Frenkel-Poole(FP) emission in low negative bias region. Analysis of reverse FPemission yielded the barrier height of trap energy level of 0.34 eV withrespect to Fermi level.