Comment by pigpop
Shortages of doctors have many causes that differ based on the country. While paying them more may help in some countries you also have to figure out how to convince doctors to live in smaller towns and cities and in less desirable provinces/states within a country. The source of the problem is that doctors are people and people have their own preferences and motivations for doing the things they do. Trying to convince even a handful of above average competency doctors to live in a remote region with bad weather and few amenities for more than a few years will be extremely difficult even if you offer them large sums of money (which aren't generally available anyways) because they have to weigh their own health and happiness in the balance when deciding where to live and practice.
If we trained a larger number of doctors market forces would reduce their price and also make more of them willing to work in less profitable places.