AlGaAs/GaAs and InAlAs/InGaAs heterostructure barrier varactors

Abstract

By the Schrödinger and Poisson equations, we have theoretically investigated AlGaAs/GaAs and InAlAs/InGaAs single barrier varactors. The energy band structure, carrier distribution, and conduction current are fully exploited for varactor design. We have explained the experimental current–voltage and capacitance–voltage measurements very well. A simple analytical model for energy band structure is derived based on the Schrödinger and Poisson equation calculation. It is found that a barrier structure of 3 nm Al0.3Ga0.7As/3 nm AlAs/3 nm Al0.3Ga0.7As for an Al0.3Ga0.7As/GaAs varactor and a barrier structure of 8 nm In0.52Al0.48As/3 nm AlAs/8 nm In0.52Al0.48As for In0.52Al0.48As/In0.47GaAs are optimal for minimal conduction currents.

Carrier conduction through the quantum barrier region in a heterostructure barrier varactor induced by an ac bias

“…We thus observe a kind of carrier confinement effect in the region of (345) 4 due to the oscillating bias. A re-distribution of the external bias is thus expected across the system.…”

“…A re-distribution of the external bias is thus expected across the system. Normally due to the high barriers in the system, the carrier density in the active region of (345) 4 is rather low (thus high resistivity), and the external dc bias applies almost linearly across region (345) 4 plus the depletion region [4]. With an ac bias, the carrier densities begin to build up at the left and right sides of the active region (Fig.…”

“…The epitaxial structure of the HBV is shown in Table 1, where the sequence of the layers is 12(345) 4 67, as the central active layer consists of four heterostructure barriers (HB). The central active layer consists of the low-doped and undoped GaAs-HB-GaAs layers.…”

Молекулярно-пучковая эпитаксия структур InGaAs/InAlAs/ AlAs для гетеробарьерных варакторов

“…Лучшие результаты для умножителей на основе ГБВ достигнуты с использо-ванием выращенных на подложках InP гетерострук-тур с несколькими последовательно расположенными барьерными слоями In 0.52 Al 0.48 As/AlAs/In 0.52 Al 0.48 As в матрице In 0.53 Ga 0.47 As, которые обеспечивают большую высоту потенциального барьера в зоне проводимости и подавление туннельных токов утечки. По результатам моделирования, выполненных в работе [5], для эф-фективного подавления туннельных токов утечки было предложено использовать в качестве оптимальной струк-туру барьера со следующей последовательностью слоев: 8 нм In 0.52 Al 0.48 As/3 нм AlAs/8 нм In 0.52 Al 0.48 As. В то же время из результатов экспериментальных исследований следует, что при указанной толщине AlAs-вставок общая оптимальная толщина барьерного слоя лежит в диапа-зоне 10−14 нм [6], что существенно меньше предсказан-ного моделью значения ∼ 19 нм.…”

Strain effect in aGaAs−In0.25Ga<

“…The ratio between the conduction/valence band offset and the energy band gap difference is normally defined as the conduction/valence band offset coefficient when studying 29,30 By applying the same numerical method of energy band structure calculations for compositionally random In 0.53 Ga 0.47 As and In 0.52 Al 0.48 As alloys as in our earlier work, 24 we have obtained a valence band offset of 0.1 eV for InAs with respect to GaAs, in good agreement with experimental data of 0.1 Ϯ0.07 eV ͑Ref. 28͒ and 0.17 eV.…”