退火对AlGaInP/GaInP多量子阱 LED外延片性能的影响

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.

Influence of Thermal Annealing to the Characteristics of A1GaInP/GaInP Multiple Quantum Wells LED Wafers

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 5×10¹⁷ cm^-3,a 0.5 μm n-(Al_0.7Ga_0.3)_0.5In_0.5P cladding layer with carrier concentration of about 3×10¹⁷ cm^-3,a (Al_0.3Ga_0.7)_0.5In_0.5P/Ga_0.5In_0.5P MQW active region,a 0.5 μm p-(Al_0.7Ga_0.3)_0.5In_0.5P cladding layer with carrier concentration of about 6×10¹⁷ cm^-3,and a 4.8 μm p-GaP current spreading layer with carrier concentration of about 5×10¹⁸ 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 5.6×10¹⁸ cm^-3 to 6.5×10¹⁸ cm^-3,and the hole carrier concentration of AlGaInP layer increased from 6.0×10¹⁷ cm^-3 to 1.1×10¹⁸ 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 8×10¹⁷ cm^-3 and 1.7×10¹⁷ 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.