This dataset contains the x-ray photoelectron spectroscopy (XPS) and electrical characterisation data used in the journal paper 'Effect of HCl cleaning on InSb–Al2O3 MOS capacitors'. The XPS data includes VAMAS files that contain the measured XPS data and modelled (fitted) components - one file for the samples treated in the HCl-water solution and a separate file for the sample treated in the HCl-IPA solution. In each file, the spectra taken after the subsequent annealing steps are included within the same VAMAS files. The XPS data folder also includes a Microsoft Excel spreadsheet, summarising the changes in the HCl-IPA sample after annealing. The electrical characterisation includes the raw measurement data and two Microsoft Excel files - one containing the data extracted from the raw capacitance-voltage data and one summarising the sample yield. The raw data includes, for each device, capacitance-voltage data, corresponding conductance-voltage data and two additional capacitance-voltage and conductance-voltage data files with reverse-direction voltage sweeps appended (where performed). For the control sample, some current-voltage data is also included. Any further enquiries regarding this dataset should be directed to o.vavasour@warwick.ac.uk