Influence of temperature and illumination on the characteristics of nanocrystalline Ga0.29 Al0.71As based heterojunction prepared by MOCVD

The heterojunction between nanocrystalline n-Ga0.29 Al0.71As and p-GaAs was fabricated by using metal organic chemical vapor deposition, MOCVD. The elemental composition of the prepared film was confirmed by energy dispersive X-ray (EDX) spectroscopy. The morphology and crystal structure of the film were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. This work explores the electrical properties of nanocrystalline n-Ga0.29 Al0.71As/p-GaAs heterojunction (HJ) in the temperature range 300–400 K. The n-Ga0.29 Al0.71As/p-GaAs heterojunction exhibits high rectifying behavior with a low saturation current density. While increasing temperature, the saturation current of the junction is increased and however, its series resistance decreased. At all temperatures the junction exhibited three types of transport mechanisms namely recombination, diffusion-limited thermionic emission, and space-charge-limited current mechanism, respectively depending on the applied bias-voltage. While increasing temperature, the diffusion potential of the barrier decreased linearly and the temperature sensitivity coefficient of the junction is found to be 5.3 mV/K. The C–V characteristics were measured at different testing signal frequencies. Their frequency dependence is related to the influence of a HJ series resistance on these characteristics. The plot of 1/C2 vs. the applied bias voltage behavior is linear, indicating the presence of abrupt junction. The effect of temperature and illumination on capacitance–voltage (C–V) characteristics of n-Ga0.29 Al0.71As/p-GaAs heterojunction was investigated. The J–V characteristics of n-Ga0.29 Al0.71As/p-GaAs heterojunction device were studied under illumination of 100 mW/cm2 at different temperature in the range 300–400 K. It can be observed that the open circuit voltage, Voc decrease continuously with increase in temperature, while Jsc increases with increase in temperature. The temperature coefficient dVoc/dT and dJsc/dT were obtained. The photovoltaic parameters are also studied under effect of different illumination intensities.

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► The preparation of nanocrystalline n-Ga 0.29 Al 0.71As using MOCVD technique was achieved.
► The J-V mechanisms are dependent on temperature and bias voltage.
► The influence temperature and illumination on the C-V characteristics were studied.
► The short circuit current of the device under illumination was enhanced.