Effects of proton bombardment on the properties of GaAs laser diodes

Gallium arsenide single-heterostructure lasers were bombarded with protons and annealed. The capacitance and threshold currents were measured. The hole concentration in the active region was calculated from the capacitance. The threshold current increased linearly with decreasing hole concentration over the range investigated. It is postulated that proton bombardment gives rise to damage centers which trap holes. These trapped holes can absorb laser radiation and it is this optical absorption which gives rise to the increased thresholds which are observed in the bombarded lasers.