摘要:

Single and double 50 Å AlAs barrier structures withn+electrode regions and 50 Å GaAs ‘‘spacer’’ layers are examined using impedance‐phase measurements, deep level transient spectroscopy (DLTS), and pulsedI–Vmeasurements. Resonant tunneling curves with a peak‐to‐valley ratio of 2:1 at 300 K are obtained from the double barrier devices. Under thermal stress of temperatures>390 K or large terminal voltage conditions, an abrupt transition from a low impedance, resistive state to a high impedance, capacitively reactive state is observed. The high impedance, reactive state is dynamically observed in all the device structures examined. In many cases, the high impedance state is persistent for extensive periods of time. Repeatable switching between the high and low persistent impedance states can be accomplished by the application of large (1–4 V) terminal voltages. However, both persistent states are stable under small applied biases for long durations. Impedance‐phase measurements have been performed on both the low impedance and the persistent high impedance state as a function of frequency for bias levels from −2.0 to 2.0 V. The low impedance state shows a much greater frequency dependence of the resistive and reactive components than the persistent high impedance state. PulsedI–Vmeasurements of Schottky barrier contacted devices reveal two characteristicI–Vcurves which are followed qualitatively for all the devices examined. The first is a series resistance limited diode with a turn‐on voltage above 1.5 V. The second characteristic, followed after the abrupt switching, is that of a diode‐like exponential current dependence on the applied voltage. Single and double barrier devices with Ohmic contacts displayed similar switching behavior at large biases. The persistent nature of the low and high impedance states observed are consistent with the formation and destruction of an inversion layer at the AlAs/GaAs interface. Silicon autodoping of the AlAs barrier regions may also give rise to DX‐like hot electron trapping, similar tothat observed in low mole fraction Al1−xGaxAs [T. N. Theis, B. D. Parker, P. M. Solomon, and S. L. Wright, Appl. Phys. Lett.49, 1542 (1986)]. The possibility of a filamentary conduction process is also discussed.

ISSN:0734-211X    

DOI:10.1116/1.584381

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

High‐performance Ga0.4In0.6As/Al0.55In0.45As pseudomorphic modulation‐doped field‐effect transistors (MODFET’s) have been further improved by replacing the Al0.48In0.52As buffer layer with an Al0.55In0.45As/Al0.41In0.59As strained‐layer superlattice (SLS) buffer layer, grown lattice matched to InP substrate by molecular‐beam epitaxy (MBE). Extrinsic transconductance as high as 306 mS/mm at 300 K has been obtained along with complete pinch off behavior for 1.7 μm gate length devices. This is attributed to the dislocation filtering and impurity gettering effects of the Al0.55In0.45As/Al0.41In0.59As SLS. Structural characterization using double crystal x‐ray diffraction also reveals the high quality of this SLS buffer layer.

ISSN:0734-211X    

DOI:10.1116/1.584382

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

We have made temperature‐dependent photoluminescence and absorption measurements of the dominant excitonic transitions in high‐quality lattice‐matched and strained single and multiple quantum well systems grown by molecular‐beam epitaxy. GaAs/AlGaAs, InGaAs/InAlAs, and InGaAs/GaAs single quantum wells grown under the optimal conditions exhibit liquid helium photoluminescence linewidths (HWHM) equal to 0.39, 3.2, and 2.7 meV, respectively. GaAs/AlGaAs multiple quantum wells of well size 60, 96, and 200 Å exhibit low‐temperature linewidth (HWHM) of 1.3, 1.6, and 2.2 meV, respectively. Strained InGaAs/AlGaAs multiple quantum wells (120 Å) have 3.5 meV HWHM linewidth. These excitonic linewidths are among the smallest reported for each system. The excitonic peaks are clearly present in all material systems up to 300 K. The finite exciton linewidth at the lowest temperature is attributed to inhomogeneous broadening due to interface roughness and well size fluctuations, while the temperature broadening results from homogeneous interactions of excitons with both acoustic and optical phonons. Based on this assumption we have calculated the homogeneous part of the linewidth and consequently the exciton lifetime at higher temperatures by careful fitting of experimental data with Gaussian and Lorentzian line shapes. The results are interpreted in terms of exciton–phonon interactions.

ISSN:0734-211X    

DOI:10.1116/1.584383

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

ISSN:0734-211X    

DOI:10.1116/1.584384

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

ISSN:0734-211X    

DOI:10.1116/1.584385

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

We have used reflection high‐energy electron diffraction (RHEED) to study the surface recovery of AlGaAs under different conditions. A modified process for growth interruptions was then introduced, where a GaAs monolayer was grown at each growth stop, and the arsenic flux was turned off during the low‐temperature phase of growth interruptions. Selectively doped inverted heterojunctions were grown using the modified growth interruptions together with low‐growth temperature (to avoid Si and impurity segregation). This combined process gave reproducible electron mobilities as high as 460 000 cm2/V s with sheet carrier concentration of 2×1011cm−2at 4.2 K.

ISSN:0734-211X    

DOI:10.1116/1.584386

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

ISSN:0734-211X    

DOI:10.1116/1.584387

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

ISSN:0734-211X    

DOI:10.1116/1.584388

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

Ga0.47In0.53As–Al0.48In0.52As high‐electron mobility transistors (HEMT’s) exhibit high transconductance and gain because of the high conductivities achievable in the structures. The effect of epitaxial layer design (spacer thickness and active channel thickness) on conductivity is examined. Device characteristics are examined as a function of active channel thickness. Reduced output conductance is observed for a 200 Å channel, but with a reduced transconductance.

ISSN:0734-211X    

DOI:10.1116/1.584389

出版商:American Vacuum Society    

年代:1988

数据来源: AIP

摘要:

A new type of AlGaAs/GaAs heterojunction bipolar transistor which employs a two‐dimensional‐hole gas base formed by planar doping using molecular‐beam epitaxy has been demonstrated. The base consists of a submonolayer of Be atoms of sheet concentration 0.5–5×1013cm−2which is deposited during growth interruption by molecular‐beam epitaxy. Transistor structures exhibit dc current gains up to 700. The effective base transit time is negligible in these transistors and it is postulated that very high speed nonequilibrium transport may occur in the collector region.

ISSN:0734-211X    

DOI:10.1116/1.584390

出版商:American Vacuum Society    

年代:1988

数据来源: AIP