Practicable Method for Estimating Thermal Depths from Phonon-Broadened Photoexcitation Cross-Section Bands. II. Analytical Representation for Neutralized Centres

摘要: The zero-phonon threshold behaviour of thermally broadened absorption cross-sections rr(hv, T) is examined for processes photoexcitation electrons and holes from deep acceptor donor levels into unperturbed Bloch states nearly parabolic conduction or valence band edge regions, respectively. In tcrms cylinder functions, analytical descriptions are given alternative photon energy dependences the transformed excitation curves e(hv, = exp (- hv/2kT) o(hv, T). Their vertex positions hv’(T) found to be shifted with respect thermal depths J(T) in question by amounts about (1 + f) 2k7; wheref 0 1, allowed forbidden transitions. A remaining uncertainty up T k7; at maximum, due possible variations electron-phonon coupling an extremely weak (vanishing) strong onc. From our assessment optical electron data Wang et al. B level GaAs Kullendorff Cue lcvel InP we conclude that 1. both transitions (f 0) dipole approximation, 2. located low temperatures 0.1 eV below middles respective gaps, 3. actual distances edges decrease (0.08 O.Ol)eV when temperature increases very room temperature. This “depth shrinkage effect” pointed out have important consequences theoretical interpretations capture properties on basis nonradiative multiphonon (NMP) mechanism. complementary hole centres appear markedly affected Rydberg-like extending several dozens meV above edges. Das Nullphononen-Schwellverhalten von thermisch verbreiterten Absorptionsquerschnitten @v, wird untersucht fur Photoanregungsprozesse Elektronen oder Lochern aus tiefen Akzeptor- bzw. Donatorniveaus ungestorte Bloch-Zustinde naherungsweise parabolischer Leitungs- Valenz