Franz–Keldysh oscillations of δ-doped GaAs

Abstract

Si-δ-doped GaAs (N2D ≊ 1011 cm−2) samples grown by molecular-beam epitaxy are investigated by using photoreflectance spectroscopy. The oscillations observed above the GaAs fundamental band gap are attributed to the Franz–Keldysh effect in the region between the δ-doped layer and the crystal surface. This ascription is confirmed by detailed studies through varying the cap thickness (250–2500 Å), temperature (10–450 K), and laser pump power (0.05–7 mW/cm2). The surface potential deduced from the Franz–Keldysh oscillations is found to be temperature and laser pump power dependent, which is explained by taking the surface photovoltaic effect into account. The surface Fermi level has been measured by this method and is found to have the value 0.73±0.02 V.

Temperature-dependent direct transition energy in Ge0.99Sn0.01 film grown on Si measured by photoreflectance spectroscopy

“…If the oscillations above the direct transition energy are the FKOs, then the period of oscillation should be changed as a function of excitation intensity due to the photovoltage effect, and it should be inversely proportional to the electric field [20][21][22]. Fig.…”

“…(1), FKO signals have extreme values. Therefore, the relationship between the FKO extreme values and ℏΩ can be expressed as [21] …”

“…The transition energy can be obtained by FKO analysis. The asymptotic expression for the FKO line shape is given by [20,21] …”

“…In contrast, when the PR spectroscopy method is used, the direct transition energy could be measured accurately without requiring a high intensity IR laser [17]. When Franz-Keldysh oscillations (FKOs) are observed in the PR spectrum, the transition energy and internal electric field could easily be obtained by using a standard FKO analysis [20][21][22].…”

Бесконтактная Характеризация Дельта-Слоев Марганца И Углерода В Арсениде Галлия

“…Ранее названный метод ак-тивно применялся в основном для исследования δ-слоев n-типа. Существует большое количество работ по ФО GaAs, δ-легированного кремнием [6][7][8][9][10]. Вместе с тем, насколько нам известно, среди δ-примесей p-типа в GaAs данным методом исследовался лишь бериллий [11,12].…”