Hot Electron Effects in Semiconductors.
The high-field transport of electrons has been calculated for two semiconductor configurations: quasi -two-dimensional and bulk. All calculations are performed by solving the Boltzmann equation, assuming a displaced Maxwellian distribution function. In the case of quasi-two-dimensional semiconductors, this treatment is applied to a <100> inversion layer in silicon. Under a high electric field, energy levels become grouped into subbands, so that motion of carriers perpendicular to the surface becomes quantized; thus, the energy, momentum and population transfer relaxation rates appropriate to the individual levels must be considered in the calculations, along with their relation to velocity overshoot. Previous work was performed under the assumption that intervalley scattering is a local phenomenon, i.e., a function only of electron temperature of the initial valley. In the present work, this assumption has been relaxed, and the intervalley coupling of electron temperature is taken into account. dc and transient response characteristics for both uncoupled and coupled models are performed, and the results are compared. Due to the recent interest in GaAs/Al(,x)Ga(,1 -x)As superlattices, there exists a need for a theory of hot electron transport in these structures. Since GaAs is a polar semiconductor, a theory must first be derived for polar III-V compounds under inversion, the result then being easily extended to superlattices. In this work, such theory is derived but, due to the alignment of the subbands, the simultaneous balance equations cannot be solved numerically with the approach undertaken here (solution of the Boltzmann equation). A theory of transport in bulk III-V compounds is modified by some simplifying approximations to make the theory numerically tractable, this theory then being applied to model bulk III-V compounds (in particular dc and transient response characteristics), along with their ternary and quaternary alloys. These results are found to compare favorably with Monte Carlo calculations.
- Pub Date:
- Physics: Condensed Matter