Ageing phenomena and determination of the optical self absorption coefficient in PN junction

¹ Département de Physique, Institut Préparatoire aux Études d'Ingénieurs de Sfax, Tunisia
² Laboratoire de Physique des Matériaux, Faculté des Sciences de Monastir, Tunisia
³ Laboratoire de Microscopie Électronique, Université Montpellier 2, France

Corresponding author: Samir.Guermazi@ipeis.rnu.tn

Received: 31 October 2000
Revised: 22 May 2001
Accepted: 5 June 2001
Published online: 15 October 2001

Abstract

We have developed a model for the calculation of the induced current due to an electron beam with an extended generation profile. The analytical expression of the electron beam induced current (EBIC) is obtained by solving the steady-state continuity equation using the Green function method. In the case of a sulphur doped (Ga_0.7Al_0.3As:N⁺/Ga_0.7Al_0.3As:P) sample prepared by metalorganic vapour phase epitaxy (MOVPE) method, the experimental current profile, measured by SEM enabled us to calculate the diffusion length of the minority carriers (L_p = 1 μm in the N region and L_n = 1.80 μm in the P region of the ternary sample). Far from the depletion layer, the experimental current profile measured provided us the optical self absorption coefficient of this sample: a_p = 1.483 μm⁻¹ in the N region and a_n = 0.167 μm⁻¹ in the P region. According to our EBIC model, the width of the depletion layer of this sample is about 0.8 μm, while at elaboration of the sample, 10 years ago, the width of the depletion layer deduced from the characteristic curve I(V) was about 300−400 Å. This widening of the depletion layer is due to the ageing of the diode.