Importance of Nonradiative Recombination Processes in Violet/UV InGaN Light Emitting Diodes

The influence of nonradiative recombination processes on the output power P of InGaN light emitting devices (LEDs) with emission wavelength between 380 and 430 nm grown on sapphire substrates have been investigated. The electroluminescence intensity was studied as a function of the forward current I and the device temperature. The P–I curves of all LEDs show a super-linear behaviour at low currents (between 80 μA and 1 mA) and a nearly linear characteristic around the operating forward current of 20 mA (equivalent to a current density of 44 A/cm2). The super-linear behaviour is attributed to the saturation of nonradiative processes which also affect the output power at operating forward current. The reduction of the output power at 20 mA with increasing temperature is correlated with the super-linear behaviour at low currents indicating that nonradiative processes are thermally activated.