Depth and lateral extension of ion milled pn junctions in CdxHg1−xTe from electron beam induced current measurements

Abstract

Ion milling has been used to convert molecular beam epitaxy vacancy-doped CdxHg1−xTe from p- to n-type. Electron beam induced current and remote electron beam induced current (REBIC) measurements have been performed to study the pn junction depth and lateral extension dependence on the milling time, milling current, and vacancy concentration. The conversion depth is linear with the milling time and current and inversely proportional to the vacancy concentration in layers thinner than 10 μm. This shows that filling of Hg vacancies in this region during conversion is limited by the rate of supply of extra Hg from the milling. The lateral extension also increases linearly with the milling time, the ratio of the lateral extension to the depth being ∼0.5. One can therefore use REBIC on the top surface to determine the junction depth, which greatly simplifies the measurement and does not destroy the diodes.

Properties of MBE Cd x Hg 1− x Te/GaAs structures modified by ion‐beam milling

“…It corresponds to the results [1,9] but it is opposite to the conclusions of [3,4,10]. Besides, in [8] any dependence of conversion depth on Cd content in active MCT layers was not observed and this does not match experimental results [11] and theoretical predictions [10].…”

“…Up to now only a small number of investigations have been made for IM of molecular beam epitaxy (MBE)-grown Сd x Hg 1-x Te layers [6 -8], although such layers are the most promising for large-format diode array manufacture, especially compound structures containing some passivation layers with high Cd content. However, according to results of [7,8], in MBE MCT layers with CdTe passivation layers, the converted depth changes linearly with milling time and is inversely proportional with vacancy concentration in layers thinner than 10 µm. This shows that the filling of Hg vacancies in this region during conversion is limited by the rate of supply of extra Hg due to the milling process.…”

HgCdTe Research at FFI: Molecular Beam Epitaxy Growth and Characterization

“…Then diodes were created by Ar ion milling through openings etched in the passivation layers, creating a p-n junction at a depth of 3.5-4 lm. 43 Cr/Au contacts were sputtered and a further 1 lm of Au was electroplated on the contact pads to avoid damage to the layer during bonding. The dynamic resistance from a 32-element linear array of such diodes with cutoff wavelength of 9.3 lm is shown in Fig.…”

Imaging one-dimensional and two-dimensional planar photodiode detectors fabricated by ion milling molecular beam epitaxy CdHgTe

“…1 Ion milling of p-type vacancy-doped CMT releases Hg atoms that diffuse into the sample and fill in Hg vacancies, thereby revealing a background n-type carrier concentration and creating a pn junction. [1][2][3][4][5][6] Experiments show that in thin layers (Ͻ10 µm), the junction depth is linear with the milling time and milling current, and inversely proportional to the vacancy concentration, 2,4,5 while for longer milling times, the conversion depth is limited by a diffusionlike process and increases as the square root of time. 3,6 These results are probably not contradictory, and can be explained in an extended diffusion model.…”