Impact of gallium concentration in the gas phase on composition of InGaAsN alloys grown by AP-MOVPE correlated with their structural and optical properties

Abstract

This work presents the epitaxial growth and material properties of InGaAsN epilayers obtained by atmospheric pressure metal organic vapour phase epitaxy. The main goal was to obtain InGaAsN quaternary alloys lattice-matched to GaAs in order to apply them as an intrinsic thick absorber in p-i-n solar cells. It allows improvement of their photovoltaic parameters (e.g. short circuit current, open circuit voltage) by reducing the density of misfit dislocations. To overcome the main difficulties connected with achieving InGaAsN composition with In/N ratio of ~ 3, which guarantees a lattice matching to GaAs, epitaxial processes were carried out with different concentration of gallium source in the gas phase. Diffraction curves, measured using HRXRD, indicated that the main aim of this work was achieved for the gas molar ratio Ga/(Ga + In) = 0.935. The optical quality and surface morphology of the investigated structures examined by PL, CER and AFM methods are also presented and discussed.Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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

“…On the other hand, the epitaxial growth of dilute nitride material is complicated, due to drastic changes in the electrical (reduction in minority carrier lifetime and their mobility [13,[25][26][27]), structural (reduction in lattice parameter [8,16,28,29]) and optical (redshift of the photoluminescence spectra and reduction in its intensity [13,17,30]) properties of the grown material as a result of N incorporation. The presence of N atoms in a semiconductor matrix induces the creation of nitrogen-related defects: interstitials (N-N) i and (N-As) i or As Ga -(N-As) i complexes, which are able to create deep traps located within the material band gap, and therefore affect the electrical properties of fabricated semiconductor devices [4][5][6][31][32][33][34][35].…”

“…GaAsN layers grown in our system exhibit a low electron concentration in the range of 10 16 cm −3 . Detailed growth parameters can be found elsewhere [5,7,16,45]. After growth, the epitaxial structure was divided into smaller parts.…”

“…The GaAsN signal located on the right side is asymmetrically broadened which might suggest inhomogeneous nitrogen distribution in GaAsN layer. Composition fluctuations in dilute nitride layers such as GaAsN or InGaAsN are well known [16,[50][51][52]. Nitrogen has a tendency to form clusters, which, together with N-related defects (for instance, (N-N) As , (N-As) As [5,35]), contribute to the formation of non-radiative recombination centers [30] and carrier localization effects [53].…”

“…Moreover, its value can be tuned by the interplay of In and N contents in the case of InGaAsN [2][3][4][5], Sb and N in the case of GaAsNSb [10,11], and Bi and N in the case of GaAsNBi [13][14][15]. Simultaneously, the latticematching of dilute nitride layers can be obtained for GaAs or Ge substrates for a particular composition with the ratio of: In to N of 3:1 [16], Sb to N of 4:1 [17] and Bi to N of 1:2 [13]. Mutual strain compensation in dilute nitrides is possible due to the presence of opposite signs of the strain component, i.e., tensile for GaAsN and compressive for InGaAs, GaAsSb and GaAsBi, respectively [18].…”