Influence Of Doping Profile Research Articles

Influence of doping profiles on coherent acoustic phonon detection and generation in semiconductors

The doping profile in different n-doped GaAs homoepitaxial structures grown by molecular beam epitaxy is investigated in the time domain by employing a laser based picosecond ultrasound technique in a contactless and noninvasive way. Experiments based on asynchronous optical sampling employ two femtosecond lasers, which allow us to detect changes in the optical reflectivity over a 1 ns time delay with a signal-to-noise ratio of 107 and 100 fs time resolution in <1 min of acquisition time. We show that the doping profile with doping densities of the order of 1018 cm−3 can be detected with picosecond ultrasound, although there is no difference in the acoustic properties of the doped and undoped region. The detection mechanism is based on a different sensitivity function for a coherent strain pulse in the doped and undoped regions. These results are corroborated by experiments at room temperature and 10 K.

Influence of doping profile on the efficiency of blue phosphorescent organic light-emitting diodes

We demonstrate that electroluminescent efficiency of blue phosphorescent organic light-emitting diodes could be improved by changing doping profile in the emissive layer (EML) of the device containing iridium(III)bis(4,6-difluorophenyl)-pyridinato-N,C2′) picolinate (FIrpic) and N,N′-dicarbazolyl-3,5-benzene (mCP). By examining the changes of recombination zone and current density with a partially doped EML, we found that most of the recombination occurred at the EML close to the electron transporting layer (ETL). Electron injection and transport were enhanced by increasing doping ratio at the EML close to the ETL and such a stepwise doping profile resulted in almost 40 % improved power efficiency compared to that of a conventional device.

Monte Carlo study of electron transport in III–V heterostructures with doped quantum wells

The transport properties of AlGaAs/GaAs/AlGaAs heterostructures with doped GaAs quantum well have been investigated by means of an ensemble Monte Carlo method. The model accounts for nonparabolicity, size quantization in all valleys, and degeneracy. The influence of doping profile, density of donors and electrons, well width, and temperature are discussed. Both steady state and transient transport have been studied, and the possibility of strong velocity overshoot has been demonstrated. The electron velocity may be strongly influenced by the spatial distribution of impurities. The choice of a doping plane located at one edge of the well allows for obtaining the highest values of mobility, static peak velocity, and maximum transient velocity. At high fields, some parasitic conduction takes place in the barriers and the transport properties are strongly affected by the characteristics of the AlGaAs layers.

Determination of the influence of doping profile on the performance of mm-wave gunn elements by using an efficient physical simulator

The influence of the doping profile on the performance of mm-wave Gunn elements is studied by applying an enhanced hydrodynamic model (HDM). According to intensive simulation results, any increase in efficiency must by attributed to a changed domain dynamic and not to a more favorable temperature distribution what had been supposed in experimental works. The results further demonstrate how to optimize the doping profile and thus give hints for an optimum design.

Efficiency versus doping profile in GaAs read-type IMPATT diodes

The influence of doping profile on the efficiency of GaAs Read-type IMPATT diodes has been studied experimentally. A diode with low breakdown voltage, or a diode with a low bias field in the drift region, gave the highest efficiency. The mechanism will be discussed, estimating the restriction of RF voltage amplitude and the change of phase relation between RF current and voltage.

Limitations of the MIS capacitance method resulting from semiconductor properties

The influence of doping profiles, traps and grain boundaries in the semiconductor on the C- V characteristics of ideal MIS diodes is calculated. In addition, it is shown that losses and frequency dispersion as well as hysteresis effects can result from traps in the semiconductor. If these semiconductor properties are ignored misinterpretations in terms of interface state density will arise which can be about 10 12 cm −2. In the case of decreasing doping profiles and traps in a n-type semiconductor one will get an apparent positive surface charge while an apparent negative surface charge will result from increasing profiles and grain boundaries. A method for the experimental determination of the C- V characteristics of ideal MIS diodes is developed. This method is applicable to stable diodes with only shallow traps in the semiconductor.