Kazutada Ikenaga

Performance of InGaN/GaN light-emitting diodes grown using NH3 with oxygen-containing impurities

The performance of InGaN/GaN light-emitting diodes (LEDs) fabricated using NH3 was varied by intentionally adding H2O, O2, or CO. The oxygen concentration in the active layer varied with the type of impurity, which was related to the binding energy of the impurity. When a small amount of oxygen was incorporated in the InGaN active layer without Si doping through an oxygen-containing impurity, the light output power of the LED was improved. On the other hand, the light output power of the LED gradually deteriorated with increasing oxygen concentration. The oxygen-containing impurities affected the light output power of the LEDs. When NH3 with any oxygen-containing impurities was purified using a purification system giving a guaranteed impurity concentration of less than 10 ppb, the light output power of the LED was recovered to that of the LED fabricated with pure NH3.

Growth of silicon-doped Al0.6Ga0.4N with low carbon concentration at high growth rate using high-flow-rate metal organic vapor phase epitaxy reactor

The relationship between the carbon concentration and electrical characteristics of silicon-doped AlGaN (Al > 0.5) was investigated using a high-flow-rate metal organic vapor phase epitaxy (MOVPE) reactor. The carbon concentration and electrical properties of AlGaN (Al > 0.5) were measured as a function of the growth rate, V/III ratio, and growth temperature. The growth rate of Al0.6Ga0.4N was linearly controlled up to 7.2 µm/h under a constant ammonia (NH3) flow rate. However, a decrease in V/III ratio resulted in an increase in carbon concentration to 8 × 1017 cm−3. With increased growth temperature, the carbon concentration decreased to less than 2 × 1017 cm−3 without showing any reduction in growth rate. As a result, n-type Al0.6Ga0.4N with a carrier concentration of 5.4 × 1018 cm−3 and a resistivity of 2.2 × 10−2 Ωcm was obtained.

Evaluation of Performance of InGaN/GaN Light-Emitting Diodes Fabricated Using NH3 with Intentionally Added H2O

We investigated the performance of InGaN/GaN light-emitting diodes (LEDs) fabricated using NH3 with intentionally added H2O. The H2O concentrations in NH3 were assessed quantitatively using an optical analyzing system. The oxygen concentration in the active layer was measured by secondary ion mass spectrometry and observed to increase with increasing H2O concentration. In addition, the oxygen was predominantly incorporated in InGaN well layers rather than in GaN barrier layers. The performance of LEDs markedly deteriorated with increasing H2O concentration. It was found by current–voltage measurement that oxygen in the multi quantum well layer increases leakage current.

High growth rate of AlGaN for buffer structures for GaN on Si to increase throughput

Throughput requirement of the epitaxial process of GaN on Si is described. The impact of the growth rate of AlGaN for the buffer layer of GaN on Si is highlighted. In the attempt of growing GaN on Si, we have tested a production scale high flow speed MOVPE reactor (TAIYO NIPPON SANSO UR25k) for 6 inch X 7 wafers. Al0.58Ga0.42N was grown with the growth rate of 1.85μm/hr at 30 kPa. AlN was grown with the growth rate of 1.4μm/hr at 13kPa. AlN/GaN SLS (5nm/20nm) was also grown at the growth rate of 1.4μm/hr. An excellent uniformity of aluminum concentration of less than 0.5% was also obtained for Al0.58Ga0.42N. The challenge which we are facing to further increase of the throughput is summarized.

Improving the light output power of DUV-LED by introducing the intrinsic last quantum barrier interlayer on the high-quality AlN template

We demonstrate that the light output power of deep ultraviolet light emitting diodes (DUV-LEDs) can be improved by introducing the intrinsic last quantum barrier interlayer on the high-quality (HQ) AlN template. With the use of HQ AlN template, the light output power of 280 nm DUV-LEDs increases about 33 % which relative to the low-quality (LQ) ones. In addition, we found the light output power can be further enhanced to 3.15 mW by inserting the intrinsic last quantum barrier interlayer.

Improvement of crystalline quality of AlN and high-Al-content AlGaN at high growth rate using horizontal high-flow-rate MOVPE system

The influences of the growth temperature of the buffer layer and the growth rate of AlN at 1300 °C on AlN crystalline quality were investigated. By using a horizontal high-flow-rate metal organic vapor phase epitaxy reactor, the growth rate of AlN was increased linearly up to 18 μm/h with increasing trimethylaluminum input partial pressure in spite of the high growth temperature of 1300 °C; the full width at half maximum of the X-ray rocking curve of AlN was almost unchanged. Moreover, the Al0.5Ga0.5N layer was grown on AlN/sapphire and the atomic step was observed on the surface of AlN and AlGaN layers by atomic force microscopy.

Criteria for versatile GaN MOVPE tool: high growth rate GaN by atmospheric pressure growth

Growth rate has a direct impact on the productivity of nitride LED production. Atmospheric pressure growth of GaN with a growth rate as high as 10 μm/h and also Al0.1Ga0.9N growth of 1 μm/h by using 4 inch by 11 production scale MOVPE are described. XRD of (002) and (102) direction was 200 arcsec and 250 arcsec, respectively. Impact of the growth rate on productivity is discussed.