Suppression of the quantum-confined Stark effect in AlxGa1−xN/AlyGa1−yN corrugated quantum wells

Abstract

We report comparative studies of 6-nm-thick Al x Ga 1Àx N/Al y Ga 1Ày N pyroelectric quantum wells (QWs) grown by plasma-assisted molecular beam epitaxy on c-sapphire substrates with a thick AlN buffer deposited under different growth conditions. The Al-rich growth conditions result in a 2D growth mode and formation of a planar QW, whereas the N-rich conditions lead to a 3D growth mode and formation of a QW corrugated on the size scale of 200-300 nm. Time-resolved photoluminescence (PL) measurements reveal a strong quantum-confined Stark effect in the planar QW, manifested by a long PL lifetime and a red shift of the PL line. In the corrugated QW, the emission line emerges 200 meV higher in energy, the low-temperature PL lifetime is 40 times shorter, and the PL intensity is stronger ($4 times at 4.5 K and $60 times at 300 K). The improved emission properties are explained by suppression of the quantum-confined Stark effect due to the reduction of the built-in electric field within the QW planes, which are not normal to the [0001] direction, enhanced carrier localization, and improved efficiency of light extraction. V C 2013 AIP Publishing LLC.[http://dx

Exciton recombination in spontaneously formed and artificial quantum wells AlxGa1‐xN/AlyGa1‐yN (x<y∼0.8)

“…To estimate the composition of the AlGaN alloy within the spontaneously formed narrow QWs we performed calculation of the heavy-hole QW excitons, using a twoparameter variational approach [24], which takes into account both elastic strain and intrinsic electric fields induced by spontaneous and piezoelectric polarizations. The calculation implied the maximal possible intrinsic electric fields, obtained in the model of a single QW inserted in infinitely wide barriers.…”

Optical Quality and Stimulated Emission of Molecular Beam Epitaxy Grown AlGaN in the Deep Ultraviolet

“…It is seen that the streaky RHEED was captured along 〈1120〉 direction, suggesting a twodimensional growth of the AlGaN layer under the metal-rich condition. [36] The optical quality of the AlGaN/AlN DH was examined at room temperature by a 213 nm laser, with a pulse width of 7 ns and a repetition rate of 100 Hz. The laser light was focused to the sample surface through a focus lens, and the emitted light was collected from the sample surface using a focus lens, which was further coupled to an optical fiber and a deep UV spectrometer.…”

“…It is seen that the streaky RHEED was captured along ⟨⟩ direction, suggesting a two‐dimensional growth of the AlGaN layer under the metal‐rich condition. [ 36 ]…”

Наноструктуры AlGaN с экстремально высоким внутренним квантовым выходом при 300 K

“…Одночастич-ные огибающие волновые функции и уровни энергии основных состояний электронов и тяжелых дырок опре-делялись методом матриц переноса. Параметры эксито-нов в КЯ рассчитывались вариационно в приближении независимых экситонов с использованием двухпарамет-рической пробной функции [12].…”