The direct epitaxial growth of high-quality III–V semiconductors on Si is a challenging materials science problem with a number of applications in optoelectronic devices, such as solar cells and on-chip lasers. We report the reduction of dislocation density in GaAs solar cells grown directly on nanopatterned V-groove Si substrates by metal–organic vapor-phase epitaxy. Starting from a template of GaP on V-groove Si, we achieved a low threading dislocation density (TDD) of 3 × 10⁶ cm^–2 in the GaAs by performing thermal cycle annealing of the GaAs followed by growth of InGaAs dislocation filter layers. This approach eliminates the need for a metamorphic buffer to directly integrate low-TDD GaAs on Si. We used these low-TDD GaAs/V-groove Si templates to grow GaAs double heterostructures that had a minority carrier lifetime of 5.7 ns, as measured by time-resolved photoluminescence, a value consistent with the material quality associated with a 20%+ efficient GaAs solar cell. However, front-junction GaAs solar cells grown on these low-TDD substrates produced a conversion efficiency of only 6.6% without an antireflection coating. Electron channeling contrast imaging measurements on this cell showed a high density of misfit dislocations at the interface between the AlInP/GaInP window layer and the GaAs absorber and between the GaAs absorber and the GaInP back surface field (BSF), likely causing a high surface recombination velocity and thus poor performance. We showed that we could reduce (and in the case of the BSF, eliminate) these dislocations by employing an AlGaAs-based window layer and BSF. Compared to GaInP, AlGaAs has dislocation glide properties that are more similar to those of GaAs, resulting in more even threading dislocation glide between layers. AlGaAs passivation improved the external quantum efficiency and open-circuit voltage of the devices, but the overall device performance was still low at an efficiency of 7.7% without an antireflection coating, likely due to cracking in the devices. This work demonstrates a route to high material quality in GaAs grown directly on Si that can be used for the production of III–V/Si optoelectronic devices.

中文翻译：

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直接在 V 型槽硅衬底上生长的 GaAs 太阳能电池


高质量 III-V 族半导体在 Si 上的直接外延生长是一个具有挑战性的材料科学问题，在太阳能电池和片上激光器等光电器件中有许多应用。我们报道了金属-有机气相外延直接在纳米图案 V 型槽 Si 衬底上生长的 GaAs 太阳能电池的位错密度降低。从 V 型槽硅上的 GaP 模板开始，我们通过对 GaAs 进行热循环退火，然后生长 InGaAs 位错滤光片层，在 GaAs 中实现了 3 ×^{10 6} cm^–2 的低螺纹位错密度 （TDD）。这种方法无需变质缓冲器即可直接在 Si 上集成低 TDD GaAs。我们使用这些低 TDD GaAs/V 槽硅模板来生长 GaAs 双异质结构，通过时间分辨光致发光测量，其少数载流子寿命为 5.7 ns，该值与与 20%+ 高效 GaAs 太阳能电池相关的材料质量一致。然而，在这些低 TDD 衬底上生长的 Front Junction GaAs 太阳能电池在没有增透膜的情况下仅产生 6.6% 的转换效率。该单元的电子通道对比成像测量显示，在 AlInP/GaInP 窗口层和 GaAs 吸收体之间以及 GaAs 吸收体和 GaInP 背表面场 （BSF） 之间的界面处存在高密度的错配位错，这可能导致较高的表面复合速度，从而产生较差的性能。我们表明，我们可以通过采用基于 AlGaAs 的窗口层和 BSF 来减少（在 BSF 的情况下，消除）这些位错。 与 GaInP 相比，AlGaAs 具有与 GaAs 更相似的位错滑光特性，从而在各层之间实现更均匀的螺纹位错滑光。AlGaAs 钝化提高了器件的外部量子效率和开路电压，但如果没有抗反射涂层，器件的整体性能仍然很低，效率为 7.7%，这可能是由于器件开裂。这项工作展示了一种直接在 Si 上生长的 GaAs 实现高材料质量的途径，可用于生产 III-V/Si 光电器件。