Electrochemical capacitance-voltage profiling of nonuniformly doped GaAs heterostructures with SQWs and MQWs for LED applications

Abstract

Light-emitting heterostructures with single and multiple GaAs/InGaAs quantum wells have been investigated by means of electrochemical capacitance-voltage (ECV) profiling. Capacitance-voltage characteristics were measured; concentration profiles of free charge carriers over the heterostructure depth as well as the intensity of quantum well filling by charge carriers were obtained. In heterostructures with a single quantum well (QW) we considered limitations of capacitance techniques for undoped QW profiling, which is situated near the metallurgic border of the p−n-junction. We made a detailed consideration of phenomena related to Debye smearing and we developed and analyzed the dependence of the space charge region width on the doping. Special attention was paid to investigation of the "blind" area. This was inspired by the practical problem from capacitance spectroscopy of semiconductors, when the researcher poses the task of obtaining a free charge carrier depth distribution profile as deep as possible in the space charge region, i.e. where the intensity of the electric field is maximum. Generally, the active QW of a LED heterostructure is placed deep in the space charge region, so reaching these regions is extremely important for practical problems. We present an evolution of capacitance-voltage characteristics during ECV profiling of nonuniformly doped p − n− heterostructures. For a heterostructure with multiple quantum wells we registered a response from 6 QWs.

Plasma-Deposited Multilayer GaP/Si p-i-n Structure for Tandem Silicon-Based Solar Cells

“…A local increase in the electron concentration is an indicator of the presence of quantum wells in the resulting structure. 25 The graph of the electron concentration profile of a structure with a width of Si layers in superlattices equal to 3 nm clearly shows one quantum well at a depth of 16 nm. There is also a shoulder at a depth of 20 nm, which corresponds to the position of the next silicon layer.…”

“…On a sample with silicon layers of 1.5 nm, there is a periodic change in the electron concentration at thicknesses of 15–22 nm with a distance between the maxima of about 3 nm, which corresponds to the geometric dimensions of the GaP/Si superlattice. A local increase in the electron concentration is an indicator of the presence of quantum wells in the resulting structure …”

Emission processes of the interaction between the quantum well and donor deltalayer in heterostructures for pHEMTs

“…The bottom inset in Figure 2 presents the concentration profile, measured in wider depth range (up to 100 mm). It is seen that after the QW response, the apparent carrier concentration monotonically decreases according to Debye smearing [11,21] while entering the semiinsulating substrate. The free carrier concentration at the level 10 10 cm −3 registered here is among the best achievements measured in semiconductors by conventional CV or ECV techniques.…”

Сквозное Концентрационное Профилирование Гетероструктурных Солнечных Элементов

“…В левой части рисунка приведен профиль распределения концентрации со стороны n + -слоя, в правой -со стороны p + -слоя. Со стороны n + -слоя, как и ожидалось согласно дебаевскому размытию [11], наблюдается монотонное снижение концентрации электронов до значения ∼ 5 • 10 15 cm −3 , соответствующего уровню легирования подложки. Со стороны p + -слоя четко зафиксированы p-и n-области, а между ними -принципиально не доступная для наблюдения так называемая " слепая зона" профилирования [11].…”

“…Со стороны n + -слоя, как и ожидалось согласно дебаевскому размытию [11], наблюдается монотонное снижение концентрации электронов до значения ∼ 5 • 10 15 cm −3 , соответствующего уровню легирования подложки. Со стороны p + -слоя четко зафиксированы p-и n-области, а между ними -принципиально не доступная для наблюдения так называемая " слепая зона" профилирования [11]. Причиной этого является инструментальное ограничение современного емкостного измерительного оборудования.…”