The III-Nitride material system offers significant potential in developing high efficiency solar cells (SC) due to their tunable bandgap (0.7 eV- 3.42 eV) with varying indium (In) concentration. Few characteristics of InGaN include wide and direct bandgap (Eg), high absorption coefficient (105 cm-1) and longer lifetimes. In this paper, InGaN/GaN SC with incorporation of GaN interlayers in absorber layer with an In content of 0.10 has been modeled and studied. InGaN is used as absorber, whereas GaN is used as window layers and strain reducing layer within the absorber layer. Increased P-GaN layer thickness increases short circuit current density (Jsc) to 2.5 mAcm-2, but lowers the open circuit voltage (Voc) to 2.11 V. GaN layer is taken to be thin enough to allow tunneling between InGaN layers and thick enough to be effective. Increase in GaN thickness increases Voc and decreases Jsc. Jsc is higher for smaller thickness of InGaN whereas Voc is higher for thicker absorber layer. The n-GaN layer thickness does not play important role in absorption of carrier. The Voc and Jsc of the device are 2.52 V and 0.653 mAcm-2, respectively.
Quantum dot (QD) confine charge carriers which results in strongly localized wave functions (WF), discrete energy eigen values and remarkable physical and novel device properties. In this paper, three-dimensional confinement regions of InN are obtained on a wetting layer (WL) in a GaN semiconducting matrix. Different structures are approximated with the influence of WL. The main objectives are: 1) To study the electronic states of single QD structure with WL and the role of their size and shape in determining the WFs and their eigen energies. 2) To study the interaction of neighboring QDs and their properties of WFs. One band Schrödinger equation in the effective mass approximation is used to compute the electronic states of QDs. Envelope function approximation with BenDaniel-Duke boundary condition is used in combination to Schrödinger equation for the calculation of eigen energies. Eigen energies are solved for the quasi-bound states using an eigenvalue study. The transfer matrix method is used to study the quantum tunneling of InN WFs, which is a direct bandgap material, through neighbor barriers of GaN material. Varying the QD radius (1nm to 8 nm) decreases the ground state energy of three structures of QD. WL thickness is increased from 0.5 nm to 3 nm which results in decrease of the eigen energies. Quasi bound state, transmission coefficient and reflection coefficient for the conical QD system are simulated. Changing the barrier width (1 nm to 3 nm) promotes higher probability of electron WF to pass through barriers. Absorption coefficient calculated for the system is 105 μm-1.
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