One of these and a MOSFET is used to form a synchronous rectifier, and four of these devices are arranged in a namesake bridge in full-wave rectifiers.  
Transferred electron devices are a form of these components that utilize negative differential resistance and are generally named for Gunn.  A law giving their current is named for transistor-inventor William Shockley.  One of these and a MOSFET is used to form a synchronous rectifier, and four of these devices are arranged in a namesake bridge in full-wave rectifiers.  If these have a large enough negative voltage drop, they go into breakdown, though reverse-bias operation is possible in their Zener variety.  For 10 points, name these devices that normally consist of a p-n junction and only allow current to pass in one direction, and which also come in light-emitting types.
Transferred electron devices are a form of these components that utilize negative differential resistance and are generally named for Gunn.  
diodes [accept early buzz of Gunn diodes]