Analysis of Current Transport Mechanism in AP-MOVPE Grown GaAsN p-i-n Solar Cell

Influence of As-N Interstitial Complexes on Strain Generated in GaAsN Epilayers Grown by AP-MOVPE

This work presents an investigation of the fully strained GaAsN/GaAs heterostructures obtained by atmospheric pressure metalorganic vapor phase epitaxy, focusing on the analysis of the strain generated in the GaAsN epilayers and its correlation with the formation of split interstitial complexes (N-As)As. We analyzed strained GaAsN epilayers with nitrogen contents and thicknesses varying from 0.93 to 1.81% and 65 to 130 nm, respectively. The composition and thickness were determined by high resolution X-ray diffraction, and the strain was determined by Raman spectroscopy, while the N-bonding configurations were determined by X-ray photoelectron spectroscopy. We found that the strain generated in the GaAsN epilayers is mainly caused by a lattice mismatch with the GaAs substrate. This macroscopic strain is independent of the amount of (N-As)As interstitial defects, while the local strain, induced by an alloying effect, tends to decrease with an increasing ratio of (N-As)As interstitial defects to substitutional nitrogen atoms incorporated into an arsenic sublattice—NAs. Here, we show experimentally, for the first time, a correlation between the strain in the GaAsN epilayers, caused by an alloying effect determined by Raman spectroscopy, and the (N-As)As/NAs ratio estimated by the XPS method. We found out that the (N-As)As interstitials compensate the local strain resulting from the presence of N in the GaAs matrix, if their amount does not exceed ~65% of the substitutional introduced nitrogen NAs.

Conduction Mechanisms in Au/0.8 nm-GaN/n-GaAs Schottky Contacts in a Wide Temperature Range

Au/0.8 nm-GaN/n-GaAs Schottky diodes were manufactured and electrically characterized over a wide temperature range. As a result, the reverse current I_inv increments from 1 × 10^-7 A at 80 K to about 1 × 10^-5 A at 420 K. The ideality factor n shows low values, decreasing from 2 at 80 K to 1.01 at 420 K. The barrier height qϕ_b grows abnormally from 0.46 eV at 80 K to 0.83 eV at 420 K. The tunnel mechanism TFE effect is the responsible for the qϕ_b behavior. The series resistance R_s is very low, decreasing from 13.80 Ω at 80 K to 4.26 Ω at 420 K. These good results are due to the good quality of the interface treated by the nitridation process. However, the disadvantage of the nitridation treatment is the fact that the GaN thin layer causes an inhomogeneous barrier height.