Quantum efficiency decay mechanism of NEA GaN photocathode: A first-principles research

Yang Shen; Liang Chen; Shuqin Zhang; Yunsheng Qian

doi:10.3788/COL201513.100401

Journals >Chinese Optics Letters >Volume 13 >Issue 10 >Page 100401 > Article

Chinese Optics Letters
Vol. 13, Issue 10, 100401 (2015)

Quantum efficiency decay mechanism of NEA GaN photocathode: A first-principles research

Yang Shen^1、*, Liang Chen^1、2、**, Shuqin Zhang¹, and Yunsheng Qian²

Author Affiliations

¹Institute of Optoelectronics Technology, China Jiliang University, Hangzhou 310018, China

²School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China

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DOI: 10.3788/COL201513.100401 Cite this Article Set citation alerts

Yang Shen, Liang Chen, Shuqin Zhang, Yunsheng Qian. Quantum efficiency decay mechanism of NEA GaN photocathode: A first-principles research[J]. Chinese Optics Letters, 2015, 13(10): 100401 Copy Citation Text

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(a) Clean (1×1) GaN(0001) surface model, (b) GaN(0001)-Cs surface model, (c) GaN(0001)-Cs-Cs surface model, (d) GaN(0001)-Cs-Cs-O surface model, (e) GaN(0001)-Cs-Cs-O-Cs surface model, (f) GaN(0001)-Cs-Cs-O-Cs-Cs surface model, and (g) GaN(0001)-Cs-Cs-O-Cs-Cs-O. The dotted lines indicate the range of each layer.

Fig. 1. (a) Clean (1×1) GaN(0001) surface model, (b) GaN(0001)-Cs surface model, (c) GaN(0001)-Cs-Cs surface model, (d) GaN(0001)-Cs-Cs-O surface model, (e) GaN(0001)-Cs-Cs-O-Cs surface model, (f) GaN(0001)-Cs-Cs-O-Cs-Cs surface model, and (g) GaN(0001)-Cs-Cs-O-Cs-Cs-O. The dotted lines indicate the range of each layer.

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Fig. 2. Variation of the photocurrent during the Cs/O activation process and stability testing of a NEA GaN photocathode.

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Fig. 3. Variation curves of the QE of a NEA GaN photocathode after 6 h of decay.

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Fig. 4. Schematic surface barrier and energy band variations of an R-mode NEA GaN photocathode before and after decay.

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Fig. 5. Formation of a [GaN (Mg): Cs] dipole and a Cs-O dipole.

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Model	a	b	c	d	e	f	g
$E_{ads}$ (eV)		0.36	7.18	9.24	0.18	0.27	2.18
$ϕ$ (eV)	4.18	2.52	2.59	6.49	1.59	1.57	2.46
$Δ ϕ$ (eV)		−1.66	+0.07	+3.90	−4.90	−0.02	+0.89

Table 1. The Calculated Values of Adsorption Energies and Work Functions for Different Surface Models, “+” Means Increment while “−” Means Decrement

Yang Shen, Liang Chen, Shuqin Zhang, Yunsheng Qian. Quantum efficiency decay mechanism of NEA GaN photocathode: A first-principles research[J]. Chinese Optics Letters, 2015, 13(10): 100401

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