In this paper, a gradient electron blocking layer (GEBL) is introduced to improve efficiency of deep‐ultraviolet light‐emitting diodes (DUV‐LEDs). Various structures of DUV‐LEDs are simulated to determine the energy band diagram variation and carrier injection mechanism resulting from the insertion of the GEBL. The simulation results show the improved electron and hole transport behavior in AlGaN multi quantum wells (MQWs). Especially, the injection efficiency of holes is improved with the increasing number of GEBL steps, which lead to the enhancement of internal quantum efficiency (IQE). The DUV‐LED structures with GEBL are grown in a high‐temperature metal‐organic chemical vapor deposition (HT‐MOCVD) system. Electroluminescence (EL) spectra show that the emission intensity at a wavelength of 280 nm from a DUV‐LED with a 12‐steps EBL is about 2.3 times that from a DUV‐LED with a single EBL.

The self-compensation effect in Si-doped Al 0.55 Ga 0.45 N layers was investigated using different SiH 4 /III ratios. The degree of compressive strain changed with SiH 4 flow rate during growth. With a low SiH 4 /III ratio of 2.46 ' 10 %6 , compressive strain was increased in comparison with the un-doped case. However, above this SiH 4 /III ratio, compressive strain decreased from ε xx = %5.07 ' 10 %3 to 4.28 ' 10 %3 when the ratio was increased to 4.1 ' 10 %5 . For higher SiH 4 /III ratios, the compressive strain again increased, which is attributed to the self-compensation effect of Si atoms. A similar tendency was observed in Photo-luminescence (PL) results. While the UV-to-violet ratio (I UV /I VL ) of room-temperature PL remained to be almost constant for SiH 4 /III ratios below 8.2 ' 10 %5 , I UV /I VL decreased rapidly above this value, as a result of self-compensation of Si atoms. These results were in good agreement with the Hall effect measurements.

No abstract