Ultrafast carrier recombination in highly n-doped Ge-on-Si films

Abstract

We study the femtosecond carrier dynamics of n-type doped and biaxially strained Ge-on-Si films which occurs upon impulsive photoexcitation by means of broadband near-IR transient absorption spectroscopy. The modeling of the experimental data takes into account the static donor density in a modified rate equation for the description of the temporal recombination dynamics. The measurements confirm the negligible contribution at a high n-type doping concentration, in the 10 19 cm À3 range, of Auger processes as compared to defect-related Shockley-Read-Hall recombination. Energy resolved dynamics reveal further insights into the doping-related band structure changes and suggest a reshaping of direct and indirect conduction band valleys to a single effective valley along with a significant spectral broadening of the optical transitions.

High carrier lifetimes in epitaxial germanium–tin/Al(In)As heterostructures with variable tin compositions

“…Correspondingly, different measurement techniques, such as temperature dependent photoluminescence, microwave reflection and transmission probing, and non-contact PCD, were developed over the years. 44,45,48,49,53,54,61,62 In this work, the minority carrier recombination properties in Ge 1Ày Sn y /InAlAs and Ge 1Ày Sn y /GaAs or AlAs heterostructures were probed at 300 K using the ultrahigh frequency microwave reflection PCD analysis at the National Renewable Energy Laboratory (NREL). The Ge 1Ày Sn y minority carrier recombination properties were studied as a function of the Ge 1Ày Sn y epilayer thickness, surface roughness, and Sn alloy composition.…”

“…Carrier lifetimes in Ge 1Ày Sn y materials are expected to increase when grown on latticematched In x Al 1Àx As intermediate buffers, wherein defects and dislocations can be reduced to negligible levels, as opposed to the direct growth of Ge 1Ày Sn y on Si. [40][41][42][43][44][45][46][47][48][49] Lattice-matched Ge 1Ày Sn y /In x Al 1Àx As heterostructures can reduce the defect induced junction leakage and increase the carrier lifetime. Two design strategies are considered here to improve the Ge 1Ày Sn y material quality compared to the direct growth on Si: (a) the thickness of the Ge 1Ày Sn y epilayer on the AlAs/GaAs substrate below the critical layer thickness, and (b) the growth of the Ge 1Ày Sn y epilayer lattice matched to In x Al 1Àx As (no thickness constraints).…”

“…Carrier lifetimes in Ge 1− y Sn y materials are expected to increase when grown on lattice-matched In x Al 1− x As intermediate buffers, wherein defects and dislocations can be reduced to negligible levels, as opposed to the direct growth of Ge 1− y Sn y on Si. 40–49…”

Влияние условий роста и уровня легирования на кинетику люминесценции слоев Ge : Sb, выращенных на кремнии

“…Последнее сильно сказывается на оценке пороговых плотностей накачки, необходимых для достижения лазерной генерации. Как показали недавние работы различных групп, посвященные измерению времен жизни носителей заряда в Ge/Si структурах [7][8][9][10][11], изначальная его оценка в 100 нс в пионерской работе [12] для сильно легированного слоя Ge/Si(001) оказалась существенно завышенной, и в действительности данные времена составляют единицы наносекунд и менее. Это сильно повышает оценку пороговой плотности накачки, необходимой для реализации лазерной генерации в слоях n-Ge [13], по сравнению с относительно оптимистичными оценками работы [12].…”