P.A. Claxton

Photoluminescence from In0.53Ga0.47As/InP quantum wells grown by molecular beam epitaxy

Room‐temperature and low‐temperature photoluminescence from quantum well In0.53Ga0.47As/InP structures grown by molecular beam epitaxy is reported for the first time. A range of well thicknesses from 240 down to 10 A was studied. Emission as short as 1.16 μm (1.07 eV) at 3.8 K and 1.22 μm (1.02 eV) at 300 K was observed from a well ∼10 A, and the overall luminescence efficiency of the structure was ∼50 times greater than that of a quaternary sample of similar carrier concentration grown by liquid phase epitaxy. The full width half‐maximum of the photoluminescence peak from a 20‐A well was 11.6 meV at 3.8 K. These results indicate the cladding InP as well as the interfaces are of very high quality.

Conduction‐band discontinuity in InGaP/GaAs measured using both current‐voltage and photoemission methods

Both current‐voltage and photoemission measurements of the conduction‐band discontinuity of the same InGaP/GaAs p‐n heterojunction have been carried out. Interpretation of the current‐voltage results using thermionic emission theory applied to a heterojunction bipolar transistor have resulted in a conduction‐band offset value of 0.21 eV in the case of a compositionally abrupt junction. This figure has been confirmed by performing independent photoemission measurements on the same junction.

Growth and characterisation of quantum wells and selectively doped heterostructures of InP/Ga0.47In0.53As grown by solid source MBE

Abstract InP/GaInAs quantum wells (QWs) have been grown by solid source MBE using the dimers As 2 and P 2 . By introducing a liquid nitrogen cooled dewar between the group V cracking zone and its mechanical shutter very good control of the As/P interface has been realised. Luminescence, absorption and excitation spectra have been used to characterise QWs and multiple QWs from which an interface fluctuation of 1 monolayer has been estimated. A selectively doped heterostructure of InP/GaInAs with a 100 A spacer layer gave a mobility of 82000 cm 2 V -1 s -1 for a charge density of 7.4×10 11 cm 2 when measured at 2 K.

Relaxation of strain within multilayer InGaAs/GaAs pseudomorphic structures

Strained‐layer superlattice structures (SLSs) have been grown in InGaAs/GaAs with various GaAs barrier layer thicknesses. Photoluminescence measurements indicate that, in structures with thin barriers, the strained layers interact leading to the relaxation of strain, even though each individual well does not exceed the critical thickness for a single quantum well. These results suggest that a fuller understanding of the mechanisms by which strain relaxes in SLSs is important in order that the constraints on the design of devices using such structures can be known.

Growth of strained InAs/InP quantum wells by molecular beam epitaxy

InAs/InP compressively strained quantum well structures with well thicknesses (LZ) 5 to 53 A have been grown by solid source molecular beam epitaxy. Relatively sharp, intense, photoluminescence (PL) is observed over the wavelength range 1.1–2.05 μm at 10 K, with linewidths as narrow as 14 meV for a 30 A well. Quantum confinement results in a shift of PL peak position of 130–710 meV with respect to the band gap of bulk strained InAs. The shifts are consistent with a conduction band offset (ΔEc) of 40%. At 300 K the wavelength range is extended to 2.23 μm, a value which to our knowledge is the longest wavelength reported for InAs/InP quantum wells. The high quality of pseudomorphic structures with well thicknesses exceeding estimates of critical layer thickness is demonstrated by transmission electron microscopy studies.

On the band gap of InGaAs/GaAs strained quantum wells

InGaAs/GaAs strained quantum wells have been grown by MBE and the effective band gap measured by photoluminescence. The measured values are compared with calculations based on a semiempirical model of the band structure. The agreement is excellent and the authors believe this relatively straight-forward theoretical technique will be of value to those engineers who require values of the band gap for device design in this and similar strained layer systems.

Bistable self-electro-optic operation of strained In0.1Ga0.9As/GaAs asymmetric Fabry Perot modulators

We report bistable operation of a strained‐layer InGaAs/GaAs asymmetric Fabry–Perot optical modulator configured as a self‐electro‐optic effect device (SEED) operating in reflection mode. Bistable loops are observed from 949 to 962 nm with switching powers down to submicrowatt levels. The contrast ratio between on and off states is as large as 5:1 (7 dB) and the device will hold in either state indefinitely. A 600‐μm‐diam device has a switching time of 20 μs for 2.1 fJ μm−2 switching energy. Large optical latch arrays are envisaged using this device.

Barrier width dependence of leakage currents in InGaAs/GaAs multiple quantum well P-I-N diodes

A range of InGaAs/GaAs strained layer multiple quantum well pin diode structures with different barrier dimensions has been grown and characterized. High quality low leakage structures (< 2 × 10−4 A/cm2 @ 0.9 VBD) with a high degree of strain (∼2%) have been produced. An important factor affecting the leakage for a fixed well composition and dimension is found to be the barrier width.

X-ray diffraction analysis of superlattices grown on misoriented substrates

Abstract X-ray diffraction curves are measured at a number of azimuth angles to determine the period of an InxGa1-xAs/InP superlattice grown on a misoriented InP substrate. It is shown that a substrate misorientation of 2.2° can cause an error as large as 7% to the calculated value of the superlattice period if the measurement is made at an arbitrary azimuth angle.

High-field hole transport in strained InxGa1-xAs/GaAs modulation-doped quantum wells

The velocity-field characteristics of holes in strained p-modulation doped InxGa1-xAs quantum wells (x=0.17 and 0.13), grown on GaAs have been measured at 77 K. Two samples at each indium fraction were studied with different doping concentrations. Saturation is almost complete at a field of 4 kV cm-1, with drift velocities of around 4.9*106 cm s-1 for the low doped samples and 3.3*106 cm s-1 for the high doped. The latter are likely to be typical of structures used for p-type field-effect transistors (FETS). The authors believe that the performance of such devices will be limited by this very low saturation velocity.