GAAS ISOTYPE DIODE PDF

HISTORY An isotype heterojunction is different from an anisotype heterojunction in that the dopants of the two sides are of the same type. It can be an n-n heterojunction or a p-p heterojunction. Discussions of the anisotype heterojunction can be found in Section 1. The first heterojunction was the anisotype, which was suggested by Shockley in , to be incorporated into the emitter-base junction to increase the current gain of a bipolar transistor.

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New Thermionic Emission and Tunneling Models in ATLAS Introduction In order to simulate heterojunction devices accurately, both the thermionic emission and tunneling mechanisms must be considered when calculating transport across hetrojunctions.

Drift-diffusion descriptions of carrier mobility are incomplete at abrupt heterointerfaces. This paper discusses the models and presents two examples of device simulation. Descriptions of the thermionic emission and tunneling across a heterointerface were presented by Yang et al. These models for thermionic emission and thermionic-field emission tunneling across a heterointerface have been incorporated into ATLAS.

Current-voltage characteristics for two devices are analyzed as a function of doping, composition and temperature and are compared to data in [1]. Current due to thermionic emission is significant for nN isotype heterojunctions. These devices show rectifying current vs. In reverse bias mode, these devices show varying levels of thermionic emission and tunneling current. Three cases were studied, varying the level of uniform doping in the second region.

The calculated conduction band profiles under a bias of Figure 1. Calculated Conduction Band Profiles for a heterojunction at In the forward bias condition, the conduction band edge of the second region AlGaAs is shifted upward, more electrons go over the barrier, hence increasing the thermionic emission. In the reverse bias condition, the electrons injected from the first region GaAs see an abrupt energy barrier whose height is determined by the conduction band discontinuity.

At higher doping densities, the peak of the conduction band approaches the Fermi level and the energy barrier becomes thinner. The increase of reverse current with increasing n-type doping in the AlGaAs predicted by the thermionic emission model can described by the lowering of the effective barrier height, hence more electrons going over the barrier. However, as the barrier thickness is reduced, the electrons with lower energy than the barrier contributes to the tunneling current.

The I-V characteristics are shown in Figure 2. Additional simulation of a pN device was performed. The current density in both forward and reverse bias conditions as a function of n-type doping was simulated. The dominant mechanism for transport was also thermionic emission.

The results are not shown. AlxGa1-xAs Graded Heterojunction Barrier The current transport of a graded isotype heterojunction barrier was studied and simulation results were compared to experimental measurements. The GaAs regions were each 0. The fractional aluminum composition was linearly graded from 0.

The conduction band profiles of the AlGaAs graded heterojunction barrier diode using the thermionic-field emission tunneling model at two biases are shown in Figure 3. In the forward bias case, the electrons are injected from region 3 to region 1 and the barrier height is reduced as the conduction band edge of region 3 moves upward. However, in the reverse bias case, the electrons from region 1 encounter an abrupt energy barrier. The electron transport across the barrier occurs either by thermionic emission over the barrier or by tunneling through it.

Since the electron energy barrier becomes more transparent under reverse bias, the tunneling process is expected to dominate as the reverse bias increases. Figure 3. Simulation and experimental measurements confirm that tunneling becomes the predominant mechanism for electron transport across the barrier in reverse bias.

Figure 4 shows the forward and reverse bias current in this device at K. The calculated results of both the thermionic emission and tunneling currents are shown. These results follow the trend of experimental results. The predicted I-V rectifying properties of this device are observable. Figure 4. The calculated thermionic emission current line and tunneling current line and crosses are both shown.

The calculated results of both the thermionic emission and tunneling currents are shown at two temperatures in Figure 5. There is good agreement between the trend of the tunneling simulation and experimental results. Similar to the nN case, the thermionic emission model significantly underestimates the reverse bias current density and tunneling becomes a dominant conduction process.

Figure 5. These models are necessary to simulate heterojunction transport accurately. Yang, J. East and G.

Haddad, Solid State Electronics, vol.

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GAAS ISOTYPE DIODE PDF

New Thermionic Emission and Tunneling Models in ATLAS Introduction In order to simulate heterojunction devices accurately, both the thermionic emission and tunneling mechanisms must be considered when calculating transport across hetrojunctions. Drift-diffusion descriptions of carrier mobility are incomplete at abrupt heterointerfaces. This paper discusses the models and presents two examples of device simulation. Descriptions of the thermionic emission and tunneling across a heterointerface were presented by Yang et al. These models for thermionic emission and thermionic-field emission tunneling across a heterointerface have been incorporated into ATLAS. Current-voltage characteristics for two devices are analyzed as a function of doping, composition and temperature and are compared to data in [1]. Current due to thermionic emission is significant for nN isotype heterojunctions.

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Fenrishicage In other projects Wikimedia Commons. Other isotyppe use isofype, e. This tells us, that the basic diode characteristics assuming that nothing happens in the space charge region must still be valid in its general form, but with one big difference that transfers into a decisive property of heterojunctions:. GaAs diodes can be used for the detection of X-rays. Some electronic properties of gallium arsenide are superior to those of silicon. Journal of Crystal Growth. In order to do that, we need to know how the discontinuities influence measurable quantities.

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