Abstract:The influence of applied electric fields on the absorption coefficient and subband distances in asymmetrical AlN/GaN coupled double quantum wells (CDQWs) has been investigated by solving Schrödinger and Poisson equations self-consistently. It is found that the absorption coefficient of the intersubband transition (ISBT) between the ground state and the third excited state (1 odd − 2even) can be equal to zero when the electric fields are applied in asymmetrical AlN/GaN CDQWs, which is related to applied electri… Show more
“…In the past few years the AlN/GaN heterostructure has attracted much attention due to high power and high frequency applications, for it has a large band gap and polarization effects. [1][2][3][4] Despite the excellent material properties, the problems such as surface sensitivity, high leakage current, and easy oxidization have restricted the performances and reliabilities of AlN/GaN devices. [5,6] It is useful to employ a suitable layer to protect the epi-layer in order to solve these problems.…”
Effects of GaN cap layer thickness on an AlN/GaN heterostructure * Zhao Jing-Tao(赵景涛) a) , Lin Zhao-Jun(林兆军) a) † , Luan Chong-Biao(栾崇彪) a) , Lü Yuan-Jie(吕元杰) b) , Feng Zhi-Hong(冯志宏) b) , and Yang Ming(杨 铭) a)
“…In the past few years the AlN/GaN heterostructure has attracted much attention due to high power and high frequency applications, for it has a large band gap and polarization effects. [1][2][3][4] Despite the excellent material properties, the problems such as surface sensitivity, high leakage current, and easy oxidization have restricted the performances and reliabilities of AlN/GaN devices. [5,6] It is useful to employ a suitable layer to protect the epi-layer in order to solve these problems.…”
Effects of GaN cap layer thickness on an AlN/GaN heterostructure * Zhao Jing-Tao(赵景涛) a) , Lin Zhao-Jun(林兆军) a) † , Luan Chong-Biao(栾崇彪) a) , Lü Yuan-Jie(吕元杰) b) , Feng Zhi-Hong(冯志宏) b) , and Yang Ming(杨 铭) a)
“…EA modulators could potentially achieve a large bandwidth and a practical optical bandwidth with a low operating energy. [2][3][4][5][6][7][8][9][10][11] Currently, several silicon-based GeSi or Ge EA modulators adopting either butting coupling or evanescent coupling are being demonstrated. [12][13][14][15][16][17] In contrast to the butting coupling mechanism, an evanescent-coupled structure is more favorable.…”
Efficient coupling from the silicon waveguide to the GeSi layer is the key to success in the GeSi electro-absorption (EA) modulator based on evanescent coupling. A lateral taper in the upper GeSi layer has room for increasing the modulating efficiency and alleviating the sensitivity of the extinction ratio (ER) and insertion loss (IL) to the length of the active region. The light behavior and the effect of the taper are explored in detail using the beam propagation method (BPM). After optimization, the light can nearly be totally confined in the GeSi layer without any oscillation. The modulator with the designed taper can achieve low IL and high ER.
Dislocation behaviors are analyzed in AlGaN/GaN multiple-quantum-well films grown with different strain-modified interlayers. In the case of multiple-quantum-well layers grown on a GaN buffer layer without the interlayer, many threading dislocations interact and annihilate within about 100 nm below the multiple quantum well layer. For multiple-quantum-well layers grown with the AlGaN interlayer, misfit dislocations between the GaN buffer layer and the AlGaN interlayer enter multiple-quantum-well layers and result in an increase of threading dislocation density. Besides misfit dislocations, the edge-type dislocation is another dislocation origin attributed to the dissociation of Shockley partials bounding the stacking fault in AlN/GaN superlattices below the interlayer interface.
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