(20 points) Carrier concentration in 2D system (a) (8 points) Derive the carrier
ID: 2291039 • Letter: #
Question
(20 points) Carrier concentration in 2D system (a) (8 points) Derive the carrier concentration in one sub-band in 2D system assuming (b) (5 points) How does the above result change if multiple sub-bands are occupied in (c) (7 points) For one sub-band assuming mDos0.5mo and temperature T 300 (a) Boltzmann statistics and (b) Fermi-Dirac statistics. the system? K, plot the carrier concentration versus (EF (Ec Esubl)). Here, Ep is the Fermi level, Ec is the bottom of the conduction band and Esubl is the sub-band energy.Explanation / Answer
b ans)
The two semiconductors of a heterojunction superlattice could be different semiconductors
such as InAs with GaP or a binary semiconductor with a ternary alloy semiconductor, such as GaAs with AlxGa1?xAs
(sometimes referred to by their slang names “Gaas” and “Algaas”). In the typical semiconductor
superlattices the periodicity d = d1 + d2 is repeated many times (e.g., 100 times).
The period thicknesses typically vary between a few layers and many layers (10?A to 500?A).
Semiconductor superlattices are today an extremely active research field internationally.
The electronic states corresponding to the heterojunction superlattices are of two fundamental
types–bound states in quantum wells and nearly free electron states in zone–folded
energy bands. In this course, we will limit our discussion to the bound states in a single
infinite quantum well. Generalizations to multiple quantum wells will be made subsequently
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