cathodoluminescence, paper review • 2

Investigating semiconductor nanowires with time-resolved cathodoluminescence

A paper using time-resolved cathodoluminescence spectroscopy was published last month in Nano Express by the group of scientists from Technical University of Braunschweig, University of Bremen and University of Giessen.

The paper entitled ‘Time-resolved cathodoluminescence investigations of AlN:Ge/GaN nanowire structures’ presents the study of different functional parts of individual AlN/GaN nanowire superlattices and their decay characteristics. With cathodoluminescence imaging, the authors are able to individually analyze the different functional parts of the nanowires.

Improving the efficiency of light-emitting diodes has a high economic and ecological potential. Particularly Blue- and white-light emitting diodes (LEDs), largely based on GaN multi-quantum-well structures, are commonly used for energy-efficient lighting. A recurring issue for the structures that are grown in the crystallographic c-direction is the quantum-confined Stark effect (QSCE) which reduces device performance. 

In their research, the authors use time-integrated and time-resolved cathodoluminescence to investigate the QCSE in GaN/AlN nanowire superlattice structures. A Delmic SPARC Spectral CL detector equipped with a streak camera for hyperspectral time-resolved measurements was used for CL measurements. The authors were able to observe a blue shift of the emitted light when going from the nanowire cap to the upper stem by selectively exciting different regions of the nanostructures. The time-resolved measurements demonstrated the shielding of the QCSE with Ge-doped samples which may be employed in the future to improve device performance in LEDs. 

The authors conclude that time-resolved cathodoluminescence is a powerful tool for investigating carrier dynamics in different parts of individual nanowires with high temporal and spatial resolution.

To read the whole paper, please access it here.

Image: Streak camera image of S2 at a sample temperature of 10 K, representing the time-resolved CL emission. The intensity of the emitted light is plotted on a logarithmic scale as a function of energy and time after excitation of the nanowire. Source: Jörgen Jungclaus et al., Nano Ex. 2 (2021)

Vera Lanskaya