Meng Hwang Liu

Carrier transport in InAs/AlSb/GaSb interband tunneling structures

A three‐band model that considers the coupling effects among the conduction band, light‐hole band, and spin‐orbit split‐off–hole band is used to investigate carrier transport in InAs/AlSb/GaSb interband tunneling structures. The E‐k relations and the boundary conditions suitable for the three‐band model are derived from the Hamiltonian. Good agreement in the peak current density and peak voltage between experiments and model has been achieved. It is also found that the three‐band model shows better agreement in the peak current densities than those of two‐band model. It indicates the importance of the coupling effects of the spin‐orbit split‐off–hole band to the InAs/AlSb/GaSb interband tunneling structures. The valley current components, the key ingredient of the peak‐to‐valley current ratios, such as the thermionic currents and hole tunneling current, are studied to fit the experimental peak‐to‐valley current ratios. It is found that the thermionic currents can be neglected due to the large band offset ...

The effect of the InAs layer thickness on the peak current density and subband properties of the GaSb/InAs/GaSb/AlSb/InAs structures

The incorporation of the InAs layer as the blocking layer into the GaSb side of the GaSb/AlSb/InAs single‐barrier interband tunneling structure resulting in a GaSb/InAs/GaSb/AlSb/InAs resonant interband tunneling structure has been proven to greatly enhance negative differential resistance peak‐to‐valley current ratios and peak current density. The role of the InAs layer induced electron and light hole coupling related to the device performance is then investigated. A three‐band model, incorporating the coupling effect of the spin‐orbit split‐off hole band, is employed to probe the effect of the InAs layer thickness on the peak current densities and the subband properties of the GaSb/InAs/GaSb/AlSb/InAs resonant interband tunneling structures. The calculated peak current densities are in reasonable agreement with the experimental data reported previously. The transmission coefficients based on the three‐band calculation can be used to interpret the variations of the peak current densities well. In addition, the ‘‘repulsion’’ of the conduction subbands in the InAs well and light‐hole subbands in the GaSb well is observed for larger InAs layer thickness. A ‘‘transition energy region’’ resulting from the crossing of the respective subbands in the InAs and GaSb wells is also observed. The effect of the InAs layer induced subband properties related to the carrier transport in the peak current of the GaSb/InAs/GaSb/AlSb/InAs structure is also discussed.

Investigation of negative differential resistance phenomena in GaSb/AlSb/InAs/GaSb/AlSb/InAs structures

The negative differential resistance (NDR) phenomena were observed in GaSb/AlSb/InAs/-GaSb/AlSb/InAs resonant interband tunnel structures. Electrons have resonantly achieved interband tunneling through the InAs/GaSb broken-gap quantum well. The InAs well width causes significant variations of the peak current density and NDR behaviors. The peak current density varies exponentially with the AlSb barrier thickness. The multiple NDR behavior was observed with appropriate InAs well and AlSb barrier thicknesses, e.g., 30 /spl Aring/ thick AlSb barrier and 240 /spl Aring/ wide InAs well. Only single negative resistance has, otherwise, been seen. The three-band model was used to interpret the effect of the InAs well and AlSb barrier on the current-voltage characteristics of GaSb/AlSb/InAs/GaSb/AlSb/InAs structures. >

Effects of inelastic scattering on interband tunneling in GaSb/AlSb/InAs/GaSb/AlSb/lnAs broken-gap interband tunneling structures

Effects of inelastic scattering on interband tunneling in GaSb/AlSb/InAs/GaSb/AlSb/InAs BGITs are investigated. The broadening mechanisms due to inelastic scattering are incorporated into the interband tunneling theory. The transmission and reflection coefficients are calculated with the aid of a three-band model, in which the conduction, light-hole, and split-off bands are coupled with one another. It is found that the inelastic scattering lowers the transmission peak and broadens the full-width at half-maximum, resulting in the decrease of the tunneling current. The calculated tunneling current due to inelastic scattering is found to have better agreement with the experiments. In addition, as the valley current plays an important role in the peak-to-valley current ratio (PVR), we then try to deduce the origin of the valley currents. The thermionic current is included in the valley current to estimate the peak-to-valley current ratio. The thermionic component from the GaSb well has important contribution to the valley current in the studied structures. The peak-to-valley current ratio is also estimated and found to have better agreement with the experiment when the inelastic scattering is considered.

The low-temperature characteristics of GaSb/AlSb/InAs/GaSb/AlSb/InAs broken-gap interband tunneling structures

The characteristics of GaSb/AlSb/InAs/GaSb/AlSb/InAs broken-gap interband tunneling structures are investigated. In addition to the main negative differential resistance peaks, kinks or small peaks can be clearly seen, especially at low temperature. The effects of the heavy-hole states are expected to play an important role. Here, a k \cdotpp model incorporating the coupling effects of the heavy-hole states is used. It is found that the kinks and small peaks are the results of heavy-hole coupling. Furthermore, the electron distribution in the InAs emitter also contributes to the phenomena observed in the low-temperature characteristics.

Interband tunneling mechanisms and effects of AlSb center-barrier layer on light particle coupling and reverse I-V characteristics of GaSb/AlSb/InAs/AlSb/GaSb/AlSb/InAs triple-barrier structures

Light particle coupling-induced tunneling has been proven to contribute to the peak current density. The overlap carrier distribution combined with the transmission coefficient is utilized to interpret the interband tunneling mechanisms. The incorporation of an AlSb layer into the GaSb/InAs interface of GaSb/AlSb/InAs/GaSb/AlSb/InAs broken-gap structures results in GaSb/AlSb/InAs/AlSb/GaSb/AlSb/InAs triple-barrier interband tunneling structures, which have been demonstrated previously. The effects of the incorporated AlSb layer on the light particle coupling are theoretically investigated with the three-band model. It was found that, while incorporating the AlSb layer into the GaSb/InAs interface, the light-particle coupling at the interface becomes weaker, and the active region finally degenerates into two separate InAs and GaSb quantum wells. In addition, the AlSb center barrier also affects the reverse I-V characteristics of the triple-barrier structures, leading to a negative differential resistance in the reverse characteristics. The effect of the AlSb center barrier on the reverse I-V characteristics of the triple-barrier structure is also discussed.

Effects of inelastic scattering on resonant interband tunneling in GaSb/AlSb/InAs/GaSb/AlSb/InAs broken-gap interband tunneling structures

Abstract Effects of inelastic scattering on interband tunneling in GaSb/AlSb/InAs/GaSb/AlSb/InAs broken-gap interband tunneling have been investigated. It is found that the interband tunneling becomes the sequential tunneling dominant due to inelastic scattering, resulting in the reduced transmission peak and the broadened full-width at half maximum. With inelastic scattering, the calculated peak current density is in better agreement with the experiments. In addition, as the valley current plays an important role in the peak-to-valley current ratio, we then try to deduce the origin of the valley currents. The thermionic current components including those from GaSb collector and GaSb well are considered to estimate the peak-to-valley current ratio. It is found that the thermionic component from the GaSb well is an important contributor to the valley current. The calculated peak-to-valley current ratio exhibits a similar variation to the experiments.

Effects of the doping levels on the characteristics of GaSb/AlSb/InAs/GaSb/AlSb/InAs broken-gap interband tunneling structures

The effects of conservation of in-plane momentum and doping levels on the low-temperature characteristics of GaSb/AlSb/InAs/GaSb/AlSb/InAs broken-gap interband tunneling structures are investigated. A three-band k p model incorporating the coupling effects among electrons, heavy holes and light holes is used to calculate the tunneling current-voltage characteristics. It is found that the kink and the small peaks in the low-temperature characteristics are results of the conservation of in-plane momentum. With a 30 A-thick InAs well, the low-temperature characteristics change from the ones with a shoulder at low doping levels to the ones with a kink at high doping levels. In addition, the peak current density decreases at high doping levels. With a 120 A-thick InAs well, the peak current density increases with increasing doping levels. Besides, the small peaks at low and medium voltages and the main current peak become more significant at high doping levels. The detailed carrier transport can be interpreted with the tunneling factors and the conservation of the in-plane momentum.

The Low-Temperature Characteristics of GaSb/AlSb/InAs/GaSb/AlSb/InAs Broken-Gap Interband Tunneling Structure

The low-temperature characteristics of GaSb/AlSb/InAVGaSb/AlSb/InAs broken-gap interband tunneling (BGIT) structures are investigated . Some small peaks and kinks are observed at the low-temperature, which are not seen at the room temperature. The heavy-hole states are expected to contribute to the additional phenomena at low temperature. An improved three-band ft.p model considering the coupling among the conduction-, light-hole and heavy-hole band is utilized to study the low temperature characteristics of the BGIT structures.

Investigation of resonant interband tunneling structures using a three-band k · p model

Abstract A three-band k · p model (CLH model) considering realistically the coupling effects among the conduction band, light-hole band and heavy-hole band is proposed to investigate further the characteristics of the resonant interband tunneling structures. The tunneling current densities for k‖-independent and -dependent cases are calculated for comparison. It is found that the inclusion of the k‖ dependence is important in the discussion of the current-voltage (I–V) characteristics. The small peaks in low temperature I–V characteristics for GaSb/AlSb/InAs/GaSb/AlSb/InAs broken-gap interband tunneling (BGIT) structure with a 120 A wide InAs well is owing to the substantial coupling between conduction band and heavy-hole band on nonzero k‖. The effects coming from the k‖ dependence also contribute to the rising of the first peak and the broading of the second peak in the low temperature I–V characteristics for BGIT structure with a 240 A wide InAs well. A CLH model can interpret the particular phenomena in the I–V characteristics that cannot be explained by the two-band model, usually used in the investigation of the interband tunneling structures.