I believe there is no comprehensive source of the information collected in a standardized way that you are looking for.
If you want to have info on a single company only, I guess your best bet is to look at the companies' annual reports. Companies disclose a lot of information about their operations there.
Some newspapers certainly did investigations on the topic and collected (spuriously, I guess) some info on that. Try to check the Wall Street Journal, the Financial Times and the Economist for the starter.
If you look for the aggregated statistics by countries, try to search the web-site www.statista.com and the works done by scientists like Gabaix and Branco Milanovic. They both did much of empirical work in inequality and could gather much info on that. No guarantee they published their datasets free of charge.