The elctrical and deep-level analysis of the low-temperature InGaAs/GaAs superlattice p-i-n structure grown by MBE

• Main Authors: Wong, Honng-Zheng, 翁宏鎮
• Other Authors: Jenn-Fang Chen
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/60203683439036021966

碩士 === 國立交通大學 === 電子物理學系 === 85 === To combine the photo-electro properties of the low temperature(LT) GaAs andthe superlattice structure, we used the molecular beam epitaxy system to growthe LT InGaAs/GaAs superlattice p-i-n structure. For comparison, the samples of the smae struectures were grown at normal temperature. We continued the research of the LT GaAs n-i-n and p-i-n structures to the electrical and deep-level measurements on the LT InGaAs/GaAs superlattice sample. The results we obtained are stated below. In the current-voltage(I-V) measurement, we observed that the leakage current of the LT sample was more than one order of magnitude higher than thatof the reference samples. A smimilar result was observed in our research of theLT GaAs p-i-n structure. It was due to the high concentration of defects in LT GaAs. Besides, at low temperarure, the LT sample had much higher turn-on voltage than the reference samples. Yet we have not found the suitable modelto explain the mechanism. Three deep levels were observed in DLTS as well as admittance spectroscopy for the LT sample. We labeled them as 91H, 91E1, and 91E2. The activation energy and corss section of 91H are 0.71eV and 1.7x10^-11cm^2.Similar deep levels as 91H were also observed in the reference samples. Therefore, this deep level was not created by the LT growth and was speculated to be the result of the lattice mismatch between InGaAs and GaAs. The activation energy and cross section of 91E2 are 0.71eV and 1.5x10^-15cm^2. This deep level was speculated to be EL2 because of its position in the Arreheniusplot and quenching effect. The activation energy and cross section of 91E1 are 0.46eV and 1.0x10^-16cm^2. It was not observed in the reference samples, suggesting that it is the uniquedeep level in the LT InGaAs/GaAs superlattice layers. The position of this deep level in the Arrehenius plot is in the vicinity of the dominating trap, 0.66eV,commonly observed in LT GaAs. This deep level may play a similar dominatingrole as the 0.66eV trap does in LT GaAs. Finally we observed unusual negative capacitance under high reverse bias or high temperature in our referencer samples by admittance spectroscopy. From theliterate, the negative capacitance is caused by the transient current. In the LT sample, there was no negatice capacitance but the capacitance increased withfrequency in the low frequency range. An activation energy obtained by takingthe inflexion points of the capacitance-frequency(C-F) curves in the low frequency range was found to correspond to 91E1. So, this deep level, 91E1, had a direct influence on the transient current of the LT InGaAs/GaAs superlattice sample.