Semiclassical density-of-states and optical-absorption analysis of amorphous semiconductors

Effects of tail states on the conduction mechanisms in silicon carbide thin films with high carbon content

“…5a. The disorder parameter for valence band tail states (E 0V ) is taken to be 1.5 times that of the conduction band (E 0 ), as it may be expected for a-Si:H films [4,15]. One could not derive an analytical expression of N(E) versus E; its simple exponentially decaying form, widely used in literature is valid only within a relatively narrow energy interval.…”

“…Ignoring the possibility of well overlap and assuming randomness of each potential well, P(U) is reasonably expected to be one sided Gaussian [15,22]: …”

“…Therefore, the most converged solution, minimum value of Eq. (15), was searched in the fitting procedure by changing initial conditions, arbitrarily (the last two data points are excluded for x = 0.42 and x = 0.59). In order to avoid potential well overlap, the width 'a' is held constant as 6 A, and the N L is limited below 10 22 cm À3 eV À1 .…”

“…The odd solutions of Schrodinger equation within such a well supplies the ground state binding energy E as [15,[19][20][21]:…”

Relationship between the optical gap and the optical-absorption tail breadth in amorphous GaAs

“…9 It is now widely held that the tail in the optical-absorption spectrum of an amorphous semiconductor is attributable to optical transitions involving tail states, these states encroaching into the otherwise empty gap region of an amorphous semiconductor. [10][11][12][13] As the tail states arise as a result of the disorder inherent to the amorphous state, the breadth of the optical-absorption tail is often taken as a direct measure of the amount of disorder present in the material. 14 In an amorphous semiconductor, such as a-GaAs, the disorder present has thermal and structural components.…”