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首页> 外文期刊>Physical review. B, Condensed Matter And Materials Physics >Effect of pulsed laser action on hole-energy spectrum of Ge/Si self-assembled quantum dots
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Effect of pulsed laser action on hole-energy spectrum of Ge/Si self-assembled quantum dots

机译：脉冲激光作用对Ge / Si自组装量子点空穴能谱的影响

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Space-charge spectroscopy has been used to study the hole energy spectrum of an array of Ge quantum dots (QD's) coherently embedded in a Si matrix and subjected to a ruby laser (λ=694 nm) nanosecond irradiation ex situ. The laser energy density in a single pulse was near the melting threshold of the Si surface. The number of laser pulses was varied from 1 to 10, and the duration of each pulse was 80 ns. From the capacitance-voltage characteristics, temperature- and frequency-dependent admittance measurements, the energies of holes confined in Ge QD's were determined. The pulsed laser annealing was found to result in a deepening of the hole energy level relative to the bulk Si valence band edge and in a decrease of the hole energy dispersion. After the treatment with ten laser pulses, the spread of the hole energies due to varying sizes of the QD's within the ensemble was reduced by a factor of about 2. The obtained results give evidence for a substantial reduction of the QD's size dispersion and for a narrowing distribution of the hole energy levels stimulated by nanosecond laser irradiation. A possible explanation of the improved uniformity of QD's sizes involves dissolving small size Ge QD's in a Si matrix by pulsed laser melting of the Ge nanoclusters and their subsequent intermixing with surrounding solid Si.
机译：空间电荷光谱已用于研究相干嵌入Ge量子点（QD）阵列的空穴能谱，该量子点被嵌入Si矩阵中，并进行红宝石激光（λ= 694 nm）的非原位辐射。单脉冲中的激光能量密度接近Si表面的熔化阈值。激光脉冲的数量从1到10不等，每个脉冲的持续时间为80 ns。从电容-电压特性，温度和频率相关的导纳测量，可以确定在Ge QD中限定的空穴的能量。发现脉冲激光退火导致相对于整体Si价带边缘的空穴能级加深并且导致空穴能散降低。经过十次激光脉冲处理后，由于量子点内整体尺寸的变化而引起的空穴能量的散布减小了约2倍。获得的结果提供了量子点尺寸散布的显着减小以及对量子点尺寸的减小的证据。缩小了纳秒激光辐照激发的空穴能级的分布。 QD尺寸均匀性改善的可能解释包括通过Ge纳米团簇的脉冲激光熔化及其随后与周围固体Si的混合将小尺寸Ge QD溶解在Si基体中。

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