Electrical performance of laser damaged silicon photodiodes

Study on the inversion of doped concentration induced by millisecond pulsed laser irradiation silicon-based avalanche photodiode

In this paper, an experimental study of silicon-based avalanche photodiode (Si-APD) with millisecond pulse laser irradiation was carried out, and the C-V curve of Si-APD was obtained by using a semiconductor analyzer. Based on the single-side abrupt junction character of n+p, combined with the corresponding theoretical derivation, the doping concentration varying with the axial depth of damaged Si-APD was obtained by inverse computation. The lattice dislocation and junction reduction were the fundamental causes of the reduced doping concentration. The research results provide a new method for the study of the internal doping concentration for detectors with millisecond pulse laser damage.

Numerical simulation of millisecond laser-induced damage in silicon-based positive-intrinsic-negative photodiode

An axisymmetric mathematical model was established for millisecond-pulsed Nd:YAG laser heating of silicon-based positive-intrinsic-negative photodiode. The transient temperature fields were obtained by using the finite element method. The temperature dependences of the material parameters and the absorption coefficient were taken into account in the calculation. The results indicate that the optical absorption coefficient and the thermal conductivity are the two key factors for the temperature evolution. The diffusion of boron in the liquid phase and the introduction of deep-level defects in the depletion region of the photodiode were the two reasons for the millisecond laser-induced electrical degradation of the photodiode. The morphological damage threshold and electrical degradation threshold of the photodiode were obtained numerically. Meanwhile, the influence of the antireflection coating, the doping concentration, and the junction depth were also considered. The results show that the morphological damage threshold decreases with adding an antireflection coating, the increase of the doping concentration, and junction depth. The electrical degradation threshold increases only with the junction depth.

Light emitting diode fault detection using p-n junction photovoltaic effect

This paper proposes an online noncontact fault detection method during light emitting diode (LED) chip packaging, which is based on the photovoltaic effect in p-n junctions. Once a LED chip bonded on a lead frame is illuminated, the photocurrent will flow through the loop circuits formed by the lead frame. Through characterization of the weak photovoltaic response in the lead frame with the 20 LED chips, five LED faults, including chip defects (chip quality and chip contamination) and bonding deficiencies (disconnection, debonding, and rebonding), can be detected before packaging. A high-sensitivity photocurrent detection instrument has been developed to detect different color (red, yellow, green, and blue) and different size LED chips (9-15 mil) on LED assembly line. A key feature of the new instrument is the capability to tune and implement the maximum output power (photocurrent) in the loop lead frame by designing the high-efficiency magnetic core, the magnetic coil and the detecting system. Experiments demonstrate that the photovoltaic behaviors for LED p-n junctions are directly related to the LED electroluminescent characteristics, and the internal optoelectronic characteristics and the external Ohmic contact performances can be derived by detecting the photocurrent of LED chips. The LED online noncontact fault detection instrument based on the photovoltaic effect can be used to substitute for the ordinary electroluminescence online contact fault detection instrument.

Laser-induced damage studies in silicon and silicon-based photodetectors

Laser-induced damage studies have been carried out on single-crystal silicon and silicon-based photodetectors, FND 100 P-I-N photodiodes, and C30954E avalanche photodiodes as a function of repetition frequency for a 1064-nm wavelength. It has been observed that the damage threshold decreases significantly when the samples are irradiated with a large number of pulses. However, this effect is evident only when the repetition frequency is greater than 1 Hz. The results are discussed in light of various existing theories.

Mechanisms for laser-induced functional damage to silicon charge-coupled imaging sensors

We measured the functional degradation of silicon CCD photodetector arrays when subjected to Nd:YAG laser irradiation at 1.06 µm by 10-ns pulses. Operational tests such as dark leakage, point-spread function, and modulation transfer function were developed for testing individual pixels and applied to the testing of locally laser-damaged CCD arrays. Testing revealed that the primary failure mechanism was the spreading of the point-spread function in the direction of clocked charge motion that resulted from a decreased depth of potential wells within the laser-damaged spot. Lesser degradation was observed at pixels near the damaged spot that were served by clock lines that traversed the damage spot. This damage behavior was correlated with decreased breakdown voltage and increased leakage current between adjacent clock lines. Subsequent morphological and TEM examination of similarly constructed chips indicated that laser heating of the polysilicon clock lines led to degradation of the adjacent isolation oxide between clock lines. Functional damage occurred at locations where two clock lines were very close to each other, and the thin oxide layer separating them was subjected to high temperatures that resulted from melting of the neighboring polysilicon.