686751 event 1764938775 1764938831 <![CDATA[Ph.D. Proposal Oral Exam - Asif Billah]]> Title:  A Multi-Scale Theoretical Study of Impurity Band Formation and Charge Transport in Doped Wurtzite Aluminum Nitride - from Shallow Donors to Deep Acceptors

Committee:

Dr. Yoder, Advisor

Dr. Doolittle, Chair

Dr. Dupuis

]]> The objective of the proposed research is to develop and validate a physics-based framework for impurity band formation and charge transport in doped wurtzite AlN. The proposed research will proceed with three goals. Goal 1 (Validation): The separable potential approach will be replaced with a partial-wave solution of the Lippmann–Schwinger equation for a single Yukawa impurity in an isotropic host. By assembling the on-shell t-matrix numerically, discrepancies will be quantified in band dispersions, bandwidths, DOS, and effective mass, thereby establishing clear quantitative error metrics for the separable method. Goal 2 (Deep acceptor band formation): A novel random lattice tight binding model will be developed for deep Be/Mg acceptors in AlN. This model, using 1s-like orbitals with no assumed periodicity and including Hartree and exchange-correlation corrections, will be used to compute band dispersions, DOS, bandwidth, and effective masses. Goal 3 (Charge transport): A Monte Carlo framework to simulate carrier dynamics will be built, using the calculated band structures as input. Transport within an acceptor band that is energetically disjoint from the host bands, treating both hopping and band-like conduction as localization weakens and the mixed regime in which the acceptor band overlaps the valence band, including microscopic scattering, temperature dependence of conductivity, resistance to freeze-out, and coupling between impurity band access regions and active device regions, will be investigated. Hence, the outcomes from these multi-scale approaches will (i) close the accuracy gap at low concentration, (ii) explain deep acceptor band formation in random lattices with many-body corrections, and (iii) link band structure to charge transport in AlN. The results will provide actionable guidance for doping targets and operating windows in high power and high frequency AlN electronics.

 

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