In the early 1960s , he jointly discovered the electron transfer mechanism ( Ridley -- Watkins -- Hilsum effect ) which underlies microwave generation in Gunn diodes .
He was the first to discover the impurity barrier mechanism for NDR , and to demonstrate electron transfer mechanism 's existence in germanium .
In the early 1960s , he jointly discovered the electron transfer mechanism ( Ridley -- Watkins -- Hilsum effect ) which underlies microwave generation in Gunn diodes , and he was the first to discover the impurity barrier mechanism for NDR , and to demonstrate its existence in germanium .