Investigation of the cleaved surface of a p-i-n laser using Kelvin probe force microscopy and two-dimensional physical simulations

We have investigated the cross-sectional electric field and potential distr ibution of a cleaved n(+)-InP/InGaAsP/p(+)-InP p-i-n laser diode using Kelv in probe force microscopy (KFM) with a lateral resolution reaching 50 nm. T he powerful characterization capabilities of KFM were compared with two-dim ensional (2D) physics-based simulations. The agreement between simulations and KFM measurements regarding the main features of the electric field and potential is very good. However, the KFM yields a voltage drop between n- a nd p-doped InP regions which is 0.4 times the one simulated. This discrepan cy is explained in terms of surface traps due to the exposure of the sample to the air and in terms of incomplete ionization. This hypothesis is confi rmed by the 2D simulations. (C) 2000 American Institute of Physics. [S0003- 6951(00)00620-3].