How can foreigners get a job as doctor in south africa

You need to apply for a critical skills visa whilst in your country. For doctors and engineers you're guaranteed for the 5 year visa. When you're now having a visa yu can now come looking for work. You'll be given up to 90 days to look for and get a job under the visa conditions.  As soon as you get a job you then notify the home affairs that you're now employed.

which is better critical skills visa or temporary residency visa??? for a person like me ???

Critical skills visa is temporary residence visa, it will only be issued till 30 days before expiry date of your passport. If passport is valid for 10 years then visa will be provided for 5 years. You can apply for permanent residence at same time when you apply for temporary residence visa.

what are the required papers for temporary residency??