GaInNAs may be used in 4-junction GaInP / sub 2 / / GaAs / GaInNAs / Ge solar cells, but its minority carrier collection length is very low. So far, the current provided by GaInNAs solar cells is not enough to improve the efficiency of 3-junction devices by adding a fourth junction. Here, we grow p-i-n GaInNAs solar cells by MBE with a wide intrinsic base layer and an internal QE close to 1.0. If the similar 1.0-ev GaInNAs junction can be successfully integrated into the 3-junction structure, the 4-junction gaas solar cell will have higher efficiency.
P-n junction diodes are modeled as three spatial regions: n-type, depletion region and p-type. Each region is distinguished by its own photoluminescence characteristics. The variation of the deviation changes the spatial boundary of the three regions; The change of excitation wavelength will change the depth of detection. The direct electron distribution of shallow junction GaAs photodiodes as a bias function is fabricated using these two variants. Special attention should be paid to the forward bias to distinguish junction voltage from terminal voltage and separate the electroluminescence effect.
Time domain terahertz waveform directly reflects the characteristic saturation and overshoot of drift current in thin depletion layer of gaas solar cell in high field, from which we can quantitatively evaluate the internal electric field. We also measured the time distribution of terahertz radiation excited by both ultrashort pulse and continuous light, and observed the decrease of the field in the depletion layer during the working process of the gaas solar cell. Since the non-linear response of the drift current in the depletion layer can be observed, we conclude that terahertz measurement provides a key technique for characterizing the performance of gaas solar cells, which can be expected under actual working conditions.
Generally, terahertz output consists of bias dependent component from drift current and bias independent component from diffusion current. Although the contribution of diffusion current in GaAs is small under the strong electric field, only 20% of the photo excited carriers contribute to the drift current, which is limited to the depletion region. On the other hand, all photo excited carriers can contribute to the diffusion current. For bias voltages greater than + 1.1 V, i.e. for very small internal electric fields, the latter contribution distorts the calibration curve.