Electrical and optical characterisation of low temperature grown InGaAs for photodiode applications

Dilute
bismide and nitride alloys are promising semiconductors for bandgap
engineering, opening additional design freedom for devices such as infrared
photodiodes. Low growth temperatures are required to incorporate bismuth or
nitrogen into III‑V semiconductors. However, the effects of low growth
temperature on dark current and responsivity are not well understood. In this
work, a set of InGaAs p‑i‑n wafers were grown at a constant temperature of 250,
300, 400 and 500 °C for all p, i and n layers. A second set of wafers was grown
where the p and n layers were grown at 500 °C while the i-layers were grown at 250, 300 and 400 °C.
Photodiodes were fabricated from all seven wafers. When constant growth
temperature was employed (for all p, i and n layers), we observed that
photodiodes grown at 500 °C show dark current density at ‑1 V that is 6 orders
of magnitude lower while the responsivity at an illumination wavelength of 1520
nm is 4.5 times higher than those from photodiodes grown at 250 °C. Results
from the second set of wafers suggest that performance degradation can be
recovered by growing the p and n layers at high temperature. For instance,
comparing photodiodes with i-layers grown at 250 °C, photodiodes showed dark
current density at -1 V that is 5 orders of magnitude lower when the p and n
layer were grown at 500 °C. Postgrowth annealing, at 595 °C for 15 minutes, on
the two wafers grown at 250 and 300 °C showed recovery of diode responsivity
but no significant improvement in the dark current. Our work suggests that
growth of the cap layer at high temperature is necessary to maintain the
responsivity and minimise the dark current degradation, offering a pathway to
developing novel photodiode materials that necessitate low growth temperatures.

稀释型铋化物与氮化物合金作为宽带隙工程中的有前景半导体材料，为红外光电二极管等器件的设计提供了额外的自由度。将铋或氮引入III-V族半导体材料的过程中，需要低生长温度。然而，低生长温度对暗电流和响应度的影響尚未得到充分理解。在本研究中，一系列InGaAs p-i-n晶圆在250°C、300°C、400°C和500°C的恒定温度下进行生长，所有p、i和n层均在同一温度下生长。另一组晶圆的生长过程中，p层和n层在500°C下生长，而i层则在250°C、300°C和400°C下生长。从所有七个晶圆中均制备了光电二极管。当采用恒定生长温度（所有p、i和n层）时，我们发现，在500°C下生长的光电二极管在-1V时的暗电流密度比在250°C下生长的二极管低六个数量级，而在1520nm照明波长下的响应度则高出4.5倍。第二组晶圆的结果表明，通过在高温下生长p和n层，可以恢复性能退化。例如，与在250°C下生长的i层的光电二极管相比，当p和n层在500°C下生长时，光电二极管在-1V时的暗电流密度降低了五个数量级。在250°C和300°C下生长的两个晶圆进行595°C、15分钟的退火处理后，二极管的响应度得到恢复，但暗电流没有显著改善。我们的研究结果表明，在高温下生长顶盖层对于维持响应度并最小化暗电流退化是必要的，为开发需要低生长温度的新型光电二极管材料提供了途径。