Detection of Nonradiative Recombination Centers in GaPN (N:0.105%) by Below‐Gap Excitation Light

Abstract

Investigation on cascade photo-excitation via intermediate band (IB) is promising for improving the efficiency of IB-type solar cells (IBSCs). Increasing nitrogen (N) concentration in GaP changes an ensemble of discrete N-N pair levels to form the IB as well as introducing defect levels acting as nonradiative recombination (NRR) centers. In continuation of detecting NRR centers in GaP 1Àx N x (x > 0.5%), a study is made for the lower N concentration region of 0.105% to understand an original formation of defect levels and their properties. Elimination of temperature quenching by immersing the sample into liquid nitrogen reveals a distribution of NRR centers inside the forbidden energy gap and the shift of Fermi energy depending on above-gap excitation (AGE) density. Profound understanding of IB and defects of GaP 1Àx N x leads to a proper optimization of IBSCs.

Detection of Nonradiative Recombination Centers in GaPN by Combining Two‐Wavelength Excited Photoluminescence and Time‐Resolved Photoluminescence

“…The tendency is consistent with the previous study. [ 36 ] The fact that the IB excitation results in higher emission efficiency than the CB excitation gives us an important clue for considering recombination process as discussed in Section 2.3.…”

“…With continuation of our study of detecting NRR centers in GaP 1-x N x with N concentrations x ¼ 0.105% and x ¼ 0.56%, [36][37][38] here we focus on detection and characterization of NRR centers at x ¼ 0.75%. A purely optical and nondestructive technique of two-wavelength excited photoluminescence DOI: 10.1002/pssb.202100119 Presence and influence of nonradiative recombination (NRR) centers in an intermediate band (IB)-type material, GaP 1-x N x (x ¼ 0.75%), are studied by twowavelength excited photoluminescence (TWEPL) method and time-resolved photoluminescence (TRPL) measurement at 77 K. With the use of below-gap excitation (BGE) light in addition to an above-gap excitation (AGE), the PL peak intensity is found to increase which indicates the presence of NRR centers and a secondary excitation from the IB to conduction band (CB).…”

“…With continuation of our study of detecting NRR centers in GaP 1— x N x with N concentrations and , [ 36–38 ] here we focus on detection and characterization of NRR centers at . A purely optical and nondestructive technique of two‐wavelength excited photoluminescence (TWEPL) method was used for the detection and characterization of NRR centers.…”

Photocurrent enhancement by below bandgap excitation in GaPN

“…GaPN alloy, which is also one of the dilute nitride semiconductors, has been rigorously studied by various techniques such as photoluminescence (PL), [11][12][13][14] time-resolved PL spectroscopy, 15) and two-wavelength excitation PL, [16][17][18][19] and spectroscopic ellipsometry 20) measurements. Contrary to the general expectation for the application of GaP (As)N to IBSC [21][22][23] in a similar way to GaAsN using the Eband as the IB, and to multijunction solar cells, [24][25][26] the present study proposes the use of two-step optical transition through the band tail states located lower than the Eband edge in GaPN as the IB.…”