Research note Determination of trap cross-section in a-Si:H p-i-n diodes parameters using simulation and parameter extraction Magali Estrada a, * , Antonio Cerdeira a , Adelmo Ortiz-Conde b,1 , Francisco Garc õa b a Secci on de Electr onica del Estado S olido, Departamento de Ingenier õa El ectrica, CINVESTAV-IPNAv. IPN No. 2508, Apto 14-740, 07300 M exico, Mexico b Laboratorio de Electr onica del Estado S olido, Universidad Sim on Bolivar, Apartado Postal 8900, Caracas 1080A, Venezuela Received 23 November 2000; received in revised form 22 December 2000 Abstract Modeling the current density±voltage J±V) curve of a-Si:H p-i-n diodes requires a group of input physical pa- rameters that have to be previously determined. Some of them can be determined directly from experiment, while others, as the trap cross-section, have to be indirectly determined or assigned. We present a simple procedure to es- timate trap cross-section using computer simulation and parameter extraction. The experimental J±V forward char- acteristic of the p-i-n diode, dark and illuminated, is used to determine the ideality factor n and the short circuit current density J SC . The charged trap cross-section and its relation to the neutral trap cross-section are determined by ®tting to tabulated and graphical results from simulation. Determined values of trap cross-section are used to simulate the re- verse current of diodes under illumination and results compared with experimental curves. Ó 2001 Elsevier Science Ltd. All rights reserved. 1. Introduction a-Si:H p-i-n diodes have been investigated as radia- tion detectors, where incident radiation can go from visible light to high energy radiation. The p-i-n diode is usually made by depositing an n -layer, followed by an intrinsic and a p -layer. The doped n - and p -layers are usually less than 400 nm, but the intrinsic i-layer) can go from tenth to tens of micrometers, in dependence of the application. Photodiodes and image sensors have up to several micrometers of i-layer, while particle and nuclear radi- ation detectors need much thicker i-layers, of tens or hundreds of micrometers. The reverse dark current at the operating voltage de®nes the threshold of detection. This dark current as well as the selection of the oper- ating voltage will depend on a high extent on the electric ®eld distribution inside the structure, which is tightly related to the density and energy distribution of local- ized states inside the mobility gap, as well as other physical parameters of the a-Si:H structure. The reverse diode current also depends on the trap cross-section. Analytical and numerical modeling of the current density±voltage J±V) characteristic of a-Si:H p-i-n have been presented in many works see e.g. Refs. [1±3]), specially related to solar cells. Simulation provides a mean to study and understand the behavior of the device and the factors that limit its eciency, if the model used to describe the device behavior is suciently precise and physical input parameters required by the simulator are known. Mobility l n and l p ); charged and neutral cross- sections of deep and tail states r Cd , r Nd , r Ct , r Nt ); ac- tivation energy of states; band gap E g and constant density of charged states at full depletion N 0 must be known. Technological and geometrical parameters are also required. Some of these parameters can be deter- mined by dierent electrical and optical measurements, Microelectronics Reliability 41 2001) 605±610 www.elsevier.com/locate/microrel * Corresponding author. E-mail address: mestrada@mail.cinvestav.mx M. Estrada). 1 On sabbatical leave from Universidad Sim on Bolivar. 0026-2714/01/$ - see front matter Ó 2001 Elsevier Science Ltd. All rights reserved. PII:S0026-271401)00005-1