1.For AlxGa1-xAs, find the composition with energy band gap 2 eV. Also find the effective mass at the Γ, X and the L valleys. Use AlxGa1-xAs = 1.42 + 1.247x. Effective mass at Γ valley is 0.067 + 0.083x; the X valley is 0.32 – 0.06x, and the L valley is 0.11 +0.03x, all in units of m*/m0 2. Consider a quantum box of GaAs of dimensions L x L x L. Assume infinite potential barriers and calculate the separation of the ground and the excited energy states as a function of L. If a separation of kBT is needed to observe the confinement effects, what is the maximum size of the L required to see these effects at 4K and at 300K. 3. A sample of GaAs has a free electron density of 1017 cm-3. Calculate the position of the Fermi level using the Boltzmann approximation and the Joyce Dixon approximation at 300K. 4. The absorption coefficients near the band edges of GaAs and Si are 104 cm-1 and 103 cm-1 respectively. What is the minimum thickness of a sample in each case that can absorb 90% of the incident light?
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