DUV-LEDs with a single EBL, graded EBL, and graded superlattice EBL were demonstrated using the high-temperature metal organic chemical vapor deposition system. A DUV-LED with a GSL-EBL showed improved carrier injection into the multi-quantum well region.
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 present study investigated the Mg doping effect in the gallium nitride (GaN) buffer layers (BLs) of AlGaN/GaN high-electron-mobility transistor (HEMT) structures grown on semi-insulating 4H-SiC substrates by metal organic chemical vapor deposition. When the Mg concentration was increased from 3 × 1017 to 8 × 1018 cm−3, the crystal quality slightly deteriorated, whereas electrical properties were significantly changed. The buffer leakage increased approximately 50 times from 0.77 to 39.2 nA at −50 V with the Mg doping concentration. The Mg-compensation effect and electron trapping effect were observed at Mg concentration of 3 × 1017 and 8 × 1018 cm−3, respectively, which were confirmed by an isolation leakage current test and low-temperature photoluminescence. When the BL was compensated, the two-dimensional electron gas (2DEG) mobility and sheet carrier concentration of the HEMTs were 1560 cm2 V−1 s−1 and 5.06 × 1012 cm−2, respectively. As a result, Mg-doped GaN BLs were demonstrated as a candidates of semi-insulating BLs for AlGaN/GaN HEMT.
Herein, the effect of crystal quality of AlN buffer layer on AlGaN/GaN/AlN double‐heterostructure high‐electron‐mobility transistor (DH‐HEMT) is investigated. The material quality of the GaN channel and the AlGaN barriers, such as the dislocation density and the interface roughness, deteriorates, and the 2D electron gas (2DEG) mobility decreases as the threading dislocation density (TDD) of the AlN buffer increases. It is also revealed that the thickness and the Al mole fraction of the AlGaN barrier are affected by the strain variation of the GaN channel depending on the TDD of the AlN buffer. The variation of the compressive strain of the GaN channel is responsible for the 2DEG density change by affecting the barrier condition and the piezoelectric polarization charge. Low‐temperature Hall effect measurement reveals that the interface roughness scattering is a dominant factor for the mobility of the DH‐HEMT, which is ≈2–6 × 103 cm2 (V s)−1.
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