Noise characteristics of bow-tie InGaAs diodes in forward and backward directions were measured in frequency range
from 10 Hz to 20 kHz at room temperature. It was found that the spectral density of voltage fluctuations changes with
frequency approximately as 1/f, indicating that origin of noise is superposition of generation and recombination
processes in defects of the structure. It was determined that the dependence of spectral density of current fluctuation on
current in backward and forward directions at different frequencies exhibits asymmetry which reflects non-uniform
electric field distribution within the structure. As both noise and sensitivity increase with bias current, optimal conditions
for device operation are discussed.
Optical and electrical noises and correlation factor between optical and electrical fluctuations of nitride-based light
emitting diodes (LEDs) have been investigated under forward bias. Their electrical, optical and noise characteristics
were compared with ones of LEDs of other materials. LED noise characteristic changes during aging have been
measured, too. It is found that optical and electrical noise spectra under forward bias for more reliable LEDs distinguish
by lower 1/f type fluctuations and Lorentzian type noise at higher frequencies. LEDs with intensive 1/f noise demonstrate
shorter lifetime. It is shown that reason of LED degradation is related with defects presence in device structure. These
defects can be formed during device fabrication or appear during operation. An analysis of LED current-voltage and
electrical noise characteristics under forward and reverse bias has shown that LEDs with intensive 1/f electrical noise,
large reverse current (low reverse breakdown voltage) and larger terminal voltage under forward bias distinguish by short lifetime.
A detailed study of photosensitivity and noise characteristics of ultrafast InGaAsP/InP avalanche photodiodes with
separate absorption, grading, charge and multiplication regions was carried out. Carrier multiplication and noise factors
were evaluated. Noise origin in investigated APDs is 1/f, generation-recombination and shot noises. Different quality
samples have been investigated and it is shown that noise characteristics well reflect APD quality problems. It is shown
that low-frequency noise and excess shot noise characteristics are very sensitive to the APD quality problems and clear
up physical processes in device structure. Noise characteristic analyses can be used for the APD quality problems
revealing and optimal design development.
Electrical and optical low frequency noise characteristics of different quality InGaAsP Fabry-Perot and distributed
feedback buried-heterostructure 1.55-μm laser diodes with the multiple-quantum-well active region are investigated
keeping in view the use of the peculiarities of the characteristics for the assessment of the quality and reliability of LDs.
The noise characteristics are shown to give the most informative result when measured at the threshold. In parallel to the
noise measurements the current-voltage characteristics are measured and analyzed. In the use of this combination an
alternative to the reliability tests by accelerated aging is seen. The mode hopping effect exhibited by the Fabry-Perot
laser diodes is suppressed by the facet coating with an antireflection layer.
A detailed study of both the optical and electrical low-frequency noise and correlation factor between optical and electrical fluctuation characteristics of single-mode multiple quantum wells (MQW) curied-heterostructure (BH) distributed feedback (DFB) laser diodes has been carried out under a wide current range. These techniques have been used to assess the structural differences between devices that exhibit superior and poor performance and reliability. It has been concluded that for the devices investigated here, the poor device performance characterstics (larger threshold current) and poor reliability are induced by the existence of defects in the interface between the active region and burying laser. These defects generate leakage currents that lead to teh larger threshold current. Defects migration during ageing forms clusters, and this leads to the poor reliability of the lasers. We demonstrate that the low-frequency noise investigations can detect the presence of defects that induce short device lifetime.
A detail study of both the optical and electrical low- frequency noise spectra and their correlation factor of graded-index separate-confinement-heterostructure, multiple quantum well strained-layer Fabri-Perot and distributed- feedback InGaAsP/InP laser diodes has been carried out under the wide current and temperature ranges. A particular attention was concentrated to the investigation of optical and electrical fluctuations due to the mode hopping effect, which was observed at specific forward currents and temperatures. Both electrical and optical noises at mode hopping areas have the Lorentzian type spectrum, and are very strongly correlated and very sensitive to temperature and facet reflectivity.