The physical mechanism of light efficiency attenuation in UVC LED chips

UVC LED chips, as an efficient and environmentally friendly ultraviolet light source, have broad application prospects in fields such as sterilization, water purification, and medical care. However, the problem of light attenuation has always been a key bottleneck restricting its development and application. A deep understanding of the physical mechanism of UVC LED chip light efficiency attenuation is of great significance for improving its performance and extending its service life

The core material of UVC LED chips is wide bandgap semiconductors, such as aluminum gallium nitride (AlGaN). The changes in the properties of the material itself are one of the important reasons for the attenuation of light efficiency

During long-term operation, AlGaN materials undergo defect evolution. During the process of crystal growth, primary defects such as vacancies and dislocations are inevitably generated, and under the action of current injection and temperature increase, these defects will migrate, aggregate, and proliferate. The movement of vacancies may form new recombination centers, while the proliferation of dislocations can increase the probability of non radiative recombination of charge carriers, resulting in a decrease in the number of charge carriers originally used for luminescence and thus reducing the light efficiency

In addition, the uneven composition of materials can also exacerbate the attenuation of light efficiency. The uneven distribution of aluminum (Al) components in AlGaN materials can cause fluctuations in the bandgap width, forming local potential wells or barriers. Carriers are captured by these local potential fields during transport, increasing the possibility of non radiative recombination and leading to a decrease in light efficiency. Moreover, uneven composition can also affect the optical properties of the material, causing a shift in the emission wavelength and further reducing the luminous efficiency of the device

UVC LED chips typically adopt a multi quantum well structure, which is a key region for achieving efficient luminescence. The quality of heterojunction interfaces has a significant impact on the performance of quantum wells

The lattice mismatch at the heterojunction interface can generate stress, and during long-term operation, the release of stress can lead to defects at the interface. These interface defects will become the recombination centers of charge carriers, causing non radiative recombination of charge carriers before they reach the quantum well, reducing the luminescence efficiency of the quantum well. Meanwhile, interface defects can also affect the transport of charge carriers between heterojunctions, increasing the transport resistance of charge carriers and further exacerbating the attenuation of light efficiency

The degradation of quantum well structures is also an important factor leading to the attenuation of light efficiency. Under the action of current and temperature, the width and depth of quantum wells will change. The increase in quantum well width will weaken the confinement effect of charge carriers, causing more charge carriers to diffuse outside the quantum well and undergo non radiative recombination; The reduction of quantum well depth will lower the probability of carrier radiative recombination, leading to a decrease in light efficiency

The electrode is a key component for current injection in UVC LED chips, and its performance degradation will directly affect the light efficiency of the chip

During long-term operation, electrode materials undergo oxidation, migration, and diffusion. The oxidation of electrodes can increase their resistance, making it difficult to inject current and reducing the operating current of the chip, thereby lowering the light output power. The migration and diffusion of electrode materials may also cause changes in electrode shape, disrupt the contact between the electrode and semiconductor material, and further affect the uniform injection of current

The degradation of Ohmic contact is also an important cause of light attenuation. Ohmic contact is the key to achieving low resistance contact between electrodes and semiconductor materials, and its quality directly affects the efficiency of current injection. During long-term work, the ohmic contact area will undergo thermal aging and chemical changes, resulting in an increase in contact resistance. The increase in contact resistance will generate more Joule heat during the injection process, which not only reduces the luminous efficiency of the chip, but also may lead to an increase in chip temperature and accelerate the degradation of other components

The working environment of UVC LED chips also has a significant impact on their light efficiency attenuation

Temperature is one of the key factors affecting the performance of UVC LED chips. Chips generate a large amount of heat during operation, and poor heat dissipation can lead to an increase in chip temperature. High temperature will exacerbate the evolution of defects in materials, the degradation of quantum well structures, and the degradation rate of electrodes and Ohmic contacts. At the same time, high temperature also increases the probability of non radiative recombination of charge carriers, reducing luminous efficiency

Humidity and corrosive gases can also have adverse effects on the performance of UVC LED chips. A high humidity environment can cause oxidation and corrosion on the surface of the chip, damaging its surface structure and affecting the efficiency of light extraction. Corrosive gases will undergo chemical reactions with chip materials, leading to material performance degradation and subsequently affecting the light efficiency of the chip

In summary, the attenuation of light efficiency in UVC LED chips is a complex physical process that involves changes in material properties, degradation of heterojunction interfaces and quantum well structures, degradation of electrode Ohmic contacts, and external environmental factors. Thoroughly studying these physical mechanisms has important guiding significance for the development of high-performance and long-life UVC LED chips. In the future, by optimizing material growth processes, improving device structure design, and enhancing packaging and heat dissipation performance, it is expected to effectively suppress the light efficiency attenuation of UVC LED chips and promote their widespread application in more fields