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Deep defect centers in high-power AlGaAs/GaAs laser diode arrays emitting at a wavelength of 808 nm are studied by Fourier-transform photocurrent spectroscopy and by electrical deep level transient spectroscopy. Different types of deep centers with binding energies between 0.15 and 0.8 eV are found in graded-index and step-index diode structures. In all structures, the defect concentration increases with operation time. We demonstrate that different operation conditions of the devices, such as regular operation or accelerated aging at increased temperatures, cause different scenarios of deep level creation. In addition to deep centers, aging leads to the formation of shallow defects and a reshaping of the absorption band edge.

We report new methods of identifying the effects of aging on the light–current (L–I) and current–voltage (I–V) characteristics of AlInGaP light-emitting diodes (LEDs). We believe that these methods are also applicable to other III–V compound semiconductors. We observe a broadening of the nonlinear range of the L–I characteristic accompanied by a shift to higher currents in the I–V characteristic. These features can be attributed to an increase of nonradiative recombination processes in the active layer. A second process, however, can lead to an increase of the LED output power. We conclude from an analysis of the current dependence that this process is due to a different mechanism.

We present the results on aging mechanisms acting in high-power laser diode arrays (LDAs) employing Fourier-transform (FT) spectroscopy. The FT spectrometer was used as an excitation source for performing photocurrent (PC) measurements in two sets of aged LDA samples. The PC spectra reveal both the evolution of a defect band located in the optically active layer as well as modifications of the interband part of the spectrum upon aging. Such changes represent sensitive quantitative measures of the aging status and provide insight into the microscopic changes of the device structure upon aging.

The authors present a detailed investigation of defects generated during catastrophic optical damage (COD) in high-power 650nm AlGaInP lasers using microphotoluminescence (μ-PL) mapping, focused ion beam (FIB) microscopy, and deep-etching techniques. High-resolution μ-PL images demonstrated that during COD, nonradiative dark line defects (DLDs) originate from the front mirror of the laser and propagate in several branches into the laser perpendicular to the output facet. Furthermore, FIB microscopy identified the epitaxial layers affected by COD, revealing that DLDs are confined to the active region. In addition, deep etching confirmed that these defects have a noncrystalline nature.

The authors report on quantitative investigations of the voltage drop across the heterostructure layer sequence of an operating AlGaInP light-emitting diode via Kelvin probe force microscopy for different external biases between −2.0 and +1.86V. In the low voltage regime, most of the voltage drops in the active layer. For bias voltages above +1.5V, however, they found an additional voltage drop on the p side of the device, which reduces the power efficiency of the light-emitting diode.

The internal quantum efficiency of (AlxGa1−x)0.5In0.5P light-emitting devices (LEDs), with an emission wavelength ranging from 650 to 560 nm, is determined by means of a model that takes into account the radiative and nonradiative recombination in the active layer, the diffusive leakage of carriers into the confining layers, and the influence of photon recycling on the light extraction efficiency. The evaluation is based on measurements of the external quantum efficiency of the LEDs as a function of the operating current and temperature. The analysis provides the wavelength dependence of both the nonradiative recombination as well as the carrier leakage.