Analytical theory for favorable defects in tunnel diodes

Tunnel diodes play a decisive role in many semiconductor devices. Energy levels in the band gap of the diodes caused by impurities or defects are responsible for the device properties, particularly for the current/voltage characteristics. We present a simple analytical theory that provides a simple estimate for the position of energy levels in the band gap of tunnel diodes that contribute the highest electrical current at yet reliable low voltages. The latter demand is crucial for the efficient functioning of multilayered solar cells. Numerical calculations in the framework of the global transfer matrix technique show that our analytical criteria are sufficiently accurate. This makes our theory a valuable tool for the optimization of devices based on tunnel diodes.