Carrier lifetime in MBE grown Si:Sb and Si:In layers measured by the transient grating method

Abstract

The carrier recombination dynamics in MBE grown silicon films, doped with Sb or In, are investigated by the transient grating method under strong pumping conditions with 35 PS laser pulses. The temporal decay of the induced gratings gives carrier lifetimes of the order 10"o-10-8 S for doping concentrations in the range lO''-IOz0 cm-3. A complementary theoretical evaluation of the lifetimes shows the importance of the different kinds of band-toband Auger recombination increases with increasing doping concentration for Sb-doped Si. For In-doped (10'7-10'8 cm-3) Si the SRH recombination via In centres dominates. The measured lifetimes agree well with the theoretical values if it is assumed that, at the doping levels, internal stress increases the light absorption coefficient for 1 = 0.53 pm by a factor of up to 2 greater than t h e pure silicon value.

Fourier transient grating in semiconductors with nonlinear carrier recombination

“…A basic description of the sinusoidal TG of excess carriers, generated as a fundamental spatial harmonic pulse, was first developed by Woerdman [9] and improved in later papers [8,[10][11][12][13][14][15][16][17][18]. After a short excitation pulse, excess carriers recombine and diffuse within the sample, eventually returning the sample to a quiescent condition.…”

“…The method using periodic spatial excitation of excess carriers led to an elegant grating technique (for review see [8]). Concentration gratings can be used in pulsed (transient) [8][9][10][11][12][13][14][15][16][17][18] and in steady-state applications [19][20][21]. Several different physical properties for read-out signals have been used for different semiconductors and probe wavelengths, including the refractive index (so-called holographic TG) [8][9][10][11][12][13][15][16][17][18], the absorption [14,17,22], the photoconductivity current [19][20][21]23], or the electron spins [24].…”

“…Concentration gratings can be used in pulsed (transient) [8][9][10][11][12][13][14][15][16][17][18] and in steady-state applications [19][20][21]. Several different physical properties for read-out signals have been used for different semiconductors and probe wavelengths, including the refractive index (so-called holographic TG) [8][9][10][11][12][13][15][16][17][18], the absorption [14,17,22], the photoconductivity current [19][20][21]23], or the electron spins [24]. Under an additional assumption of local space charge neutrality, the sinusoidal TG erasure time has ‡ On leave from Vilnius University (e-mail: vytas@ele.kth.se and/or vytautas.grivickas@FF.vu.lt).…”

“…In the experiments discussed above, the sinusoidal profile is a reasonable approximation for the carriers generated instantaneously by short pulses, either using a light interference pattern [8][9][10][11][12][13][15][16][17][18][19][20][21][22] or a single pulse projected through a semitransparent grating [1,15,25,26]. Although nonlinear recombination could be present in these experiments, it was commonly assumed that a sinusoidal approximation may still provide an estimation which is valid at small grating periods for obtaining the transport parameters [8-12, 16, 27].…”