• S Dasgupta

      Articles written in Pramana – Journal of Physics

    • Dependence of adiabatic population transfer on pulse profile

      S Dasgupta T Kushwaha D Goswami

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      Control of population transfer by rapid adiabatic passage has been an established technique wherein the exact amplitude profile of the shaped pulse is considered to be insignificant. We study the effect of ultrafast shaped pulses for two-level systems, by density-matrix approach. However, we find that adiabaticity depends simultaneously on pulse profile as well as the frequency modulation under non-resonant conditions

    • Estimation of various scattering parameters and 2-DEG mobilities from electron mobility calculations in the three conduction bands 𝛤, L and X of gallium arsenide

      Sonal Singhal A K Saxena S Dasgupta

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      The electron drift mobility in 𝛤 conduction band of GaAs has been calculated before, but for the first time, we have made attempts to estimate the electron mobilities in higher energy L and X minima. We have also calculated the value of mobility of two-dimensional electron gas needed to predict hetero-structure device characteristics using GaAs. Best scattering parameters have been derived by close comparison between experimental and theoretical mobilities. Room temperature electron mobilities in 𝛤, L and X valleys are found to be nearly 9094, 945 and 247 cm2 /V-s respectively. For the above valleys, the electron masses, deformation potentials and polar phonon temperatures have been determined to be (0.067, 0.22, 0.39m 0 ), (8.5, 9.5, 6.5 eV), and (416, 382, 542 K) as best values, respectively. The 2-DEG electron mobility in 𝛤 minimum increases to $1.54 \times 10^{6}$ from $1.59 \times 10^{5}$ cm2 /V-s (for impurity concentration of 1014 cm-3) at 10 K. Similarly, the 2-DEG electron mobility values in L and X minima are estimated to be $2.28 \times 10^{5}$ and $1.44 \times 10^{5}$ cm2 /V-s at 10 K, which are about $\sim 4.5$ and $\sim 3.9$ times higher than normal value with impurity scattering present.

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