退火对AlGaInP/GaInP多量子阱LED外延片性能的影响

Influence of Thermal Annealing to the Characteristics of AlGaInP/GaInP Multiple Quantum Wells LED Wafers

采用LP MOCVD技术在n GaAs衬底上生长了AlGaInP/GaInP多量子阱红光LED外延片。研究表明退火对外延片性能有重要影响。与未退火样品相比,460℃退火15min,外延片p型GaP层的空穴浓度由5.6×1018cm-3增大到6.5×1018cm-3,p型AlGaInP层的空穴浓度由6.0×1017cm-3增大到1.1×1018cm-3。但退火温度为780℃时,p型GaP层和p型AlGaInP层的空穴浓度分别下降至8×1017cm-3和1.7×1017cm-3,且Mg原子在AlGaInP系材料中的扩散加剧,导致未掺杂AlGaInP/GaInP多量子阱呈现p型电导。在460～700℃退火范围内,并没有使AlGaInP/GaInP多量子阱的发光性能发生明显变化。但退火温度为780℃时,AlGaInP/GaInP多量子阱的发光强度是退火前的2倍。

The AlGaInP/GaInP multiple quantum wells red LED wafers were grown by EMCORE GS/3200 LP-MOCVD. Properties of these wafers were investigated by ECV and photoluminescence measurements. The influences of thermal annealing on the characteristics of AlGaInP/GaInP multiple quantum wells LED wafers were studied. The AlGaInP/GaInP multiple quantum wells LED wafer for thermal annealing experiments consisted of a 0.5 μm n-GaAs buffer layer with carrier concentration of about 5×10^(17) cm^(-3), a 0.5 μm n-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P cladding layer with carrier concentration of about 3×10^(17) cm^(-3), a (Al_(0.3)Ga_(0.7))_(0.5)In_(0.5)P/Ga_(0.5)In_(0.5)P MQW active region, a 0.5 μm p-(Al_(0.7)Ga_(0.3))_(0.5)In_(0.5)P cladding layer with carrier concentration of about 6×10^(17) cm^(-3), and a 4.8 μm p-GaP current spreading layer with carrier concentration of about 5×10^(18) cm^(-3). The wafer was split into six pieces. These six pieces were annealed under different temperatures within 460～780 ℃ respectively for 15 min in nitrogen.Compared with as grown samples, the hole carrier concentration of GaP layer in LED wafer increased from 5.6×10^(18) cm^(-3) to 6.5×10^(18) cm^(-3), and the hole carrier concentration of AlGaInP layer increased from 6.0×10^(17) cm^(-3) to 1.1×10^(18) cm^(-3), when wafer was annealed under 460 ℃ for 15 min in nitrogen. The hole carrier concentration of GaP and AlGaInP layers did not obviously change when the annealed temperature was increased to 700 ℃. However, the hole carrier concentration of GaP layer and AlGaInP layer decreased to 8×10^(17) cm^(-3) and 1.7×10^(17) cm^(-3) when wafer was annealed under 780 ℃ for 15 min. And the diffusibility of Mg atoms was enhanced and the undoped AlGaInP/GaInP MQW was p type conductance when the annealing temperature increased to 780 ℃. The peak wavelength and FWHM did not obviously change when the annealing temperature was lower than 780 ℃. However, the PL peak intensity from MQW was about 2 times stronger than that of as grown sample when wafer was annealed under 780 ℃ for 15 min.