Interfacial characteristics of Ga0.51In0.49P/GaAs heterostructures grown by metal-organic vapor-phase epitaxy in the temperature range from 600 °C to 730 °C were studied. Photoluminescence (PL) measurements have been used for this purpose. A PL peak with an energy of about 1.425 eV (870 nm) was continuously observed in samples containing the GaInP-to-GaAs interface. Excitation power dependent PL measurements show that this peak belongs to an excitonic recombination. Furthermore, a strong blue-shift of this PL-peak energy was observed as the excitation power increased. We attribute the 870 nm peak to the radiative recombination of spatially separated electron-hole pairs and suggest the type-II band alignment at the ordered GaInP to GaAs heterointerface under growth conditions reported here. Further investigations using x-ray diffraction measurements and simulations with dynamical theory show that the lower and upper interfaces are not equivalent. This explains the absence of type-II transition in most GaAs-to-GaInP lower interfaces.

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Photoluminescence analysis of Ga0.51In0.49P/GaAs single-quantum well structures grown by metal-organic vapor-phase epitaxy in the temperature range from 570 to 720 °C have been carried out. Besides the GaAs band-edge emissions, all SQW samples studied here exhibit a dominant long-wavelength peak, which is attributed to the spatially indirect transition due to the type-II band alignment of Ga0.51In0.49P/GaAs heterojunctions. The energy of the type-II PL emission has been found to depend strongly on the growth temperature indicating the strong influence of the growth temperature on the band alignment. The shifts of the type-II PL emission have been used to estimate the growth temperature dependent conduction and valence band discontinuity of the Ga0.51In0.49P/GaAs heterojunction. X-ray diffraction measurements and simulations using the dynamical theory were carried out to study the influence of the growth temperature on the unintended interfacial layers.

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A completely integrated, WiMedia/MBOA-compliant [1] RF transceiver for Ultra-Wideband (UWB) data communication in the 3 to 5GHz band is presented. It is designed in 0.13µm standard CMOS technology for a single supply voltage of 1.5V. The measured noise figure (NF) of 3.6 to 4.1dB over all three bands is significantly better (2 to 4dB) than existing CMOS [2] or BiCMOS SiGe [3] receive chains, and comparable to the BiCMOS SiGe receiver described in [4]. On the transmit side, an improvement in P 1dB of 15dB compared to [2] is achieved, supporting an EVM of -28dB up to -4dBm output power. This output power level is required to support realistic external losses.The block diagram of the direct conversion transceiver chip is shown in Fig. 6.5.1. The fully differential receiver includes an LNA with high-and low-gain modes and a programmable-gain amplifier (PGA) with 4 gain steps to enable optimum receive performance for different signal strengths and interferer scenarios [5]. The amplifiers are followed by a Gilbert-type down-conversion mixer, which generates quadrature (I and Q) outputs. It is based on a class-AB voltage-to-current converter, a Gilbert Quad, and a load that implements both a current-to-voltage converter and a low-noise filter used to suppress large out-of-band interferers. The position of the filter poles (around 500MHz) can be calibrated digitally by tuning filter capacitors, thus achieving good transition-band and stop-band accuracy in the presence of process variations. The analog I/Q chip interface is driven by an output buffer with a bandwidth of 1GHz to enable characterization of all receive chain impairments.On the TX side the baseband I/Q analog input signal is converted to a current by a highly linear voltage-to-current converter and fed into Gilbert-type folded upconverting mixers. To reduce the LO leakage caused by dc offset in the mixer stage, a compensation DAC is added and controlled by a serial interface bus. The differential output signal of the mixer is converted to single ended, followed by a programmable gain stage and an integrated 3-stage power amplifier (PA). The 3 required coils in the PA are realized by stacked inductors. Gain-switching is implemented by a capacitive divider with a switchable divider ratio, yielding a variable gain range of 30dB with a resolution of 1dB for high-gain settings. A power detector followed by an ADC with 6b resolution is implemented to measure the output voltage of the PA. Taking into account some back-off due to external losses, antenna and impedance mismatch, this scheme enables cost-efficient control of the actual output power to fulfill TX emission-mask requirements without external components. Figure 6.5.2 shows the block diagram of the LO generation. To generate the three required LO frequencies of 3.432, 3.960 and 4.488GHz with minimal transition time when hopping, an openloop topology is required.The principle idea is to add or subtract a low frequency (±264MHz or -792MHz) from a fixed frequency of 4.224GHz. The proposed implementation includ...